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This is libc.info, produced by makeinfo version 5.2 from libc.texinfo.
This file documents the GNU C Library.
This is 'The GNU C Library Reference Manual', for version 2.19
(Buildroot).
Copyright (C) 1993-2014 Free Software Foundation, Inc.
Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.3 or
any later version published by the Free Software Foundation; with the
Invariant Sections being "Free Software Needs Free Documentation" and
"GNU Lesser General Public License", the Front-Cover texts being "A GNU
Manual", and with the Back-Cover Texts as in (a) below. A copy of the
license is included in the section entitled "GNU Free Documentation
License".
(a) The FSF's Back-Cover Text is: "You have the freedom to copy and
modify this GNU manual. Buying copies from the FSF supports it in
developing GNU and promoting software freedom."
INFO-DIR-SECTION Software libraries
START-INFO-DIR-ENTRY
* Libc: (libc). C library.
END-INFO-DIR-ENTRY
INFO-DIR-SECTION GNU C library functions and macros
START-INFO-DIR-ENTRY
* ALTWERASE: (libc)Local Modes.
* ARGP_ERR_UNKNOWN: (libc)Argp Parser Functions.
* ARG_MAX: (libc)General Limits.
* BC_BASE_MAX: (libc)Utility Limits.
* BC_DIM_MAX: (libc)Utility Limits.
* BC_SCALE_MAX: (libc)Utility Limits.
* BC_STRING_MAX: (libc)Utility Limits.
* BRKINT: (libc)Input Modes.
* BUFSIZ: (libc)Controlling Buffering.
* CCTS_OFLOW: (libc)Control Modes.
* CHILD_MAX: (libc)General Limits.
* CIGNORE: (libc)Control Modes.
* CLK_TCK: (libc)Processor Time.
* CLOCAL: (libc)Control Modes.
* CLOCKS_PER_SEC: (libc)CPU Time.
* COLL_WEIGHTS_MAX: (libc)Utility Limits.
* CPU_CLR: (libc)CPU Affinity.
* CPU_ISSET: (libc)CPU Affinity.
* CPU_SET: (libc)CPU Affinity.
* CPU_SETSIZE: (libc)CPU Affinity.
* CPU_ZERO: (libc)CPU Affinity.
* CREAD: (libc)Control Modes.
* CRTS_IFLOW: (libc)Control Modes.
* CS5: (libc)Control Modes.
* CS6: (libc)Control Modes.
* CS7: (libc)Control Modes.
* CS8: (libc)Control Modes.
* CSIZE: (libc)Control Modes.
* CSTOPB: (libc)Control Modes.
* DES_FAILED: (libc)DES Encryption.
* DTTOIF: (libc)Directory Entries.
* E2BIG: (libc)Error Codes.
* EACCES: (libc)Error Codes.
* EADDRINUSE: (libc)Error Codes.
* EADDRNOTAVAIL: (libc)Error Codes.
* EADV: (libc)Error Codes.
* EAFNOSUPPORT: (libc)Error Codes.
* EAGAIN: (libc)Error Codes.
* EALREADY: (libc)Error Codes.
* EAUTH: (libc)Error Codes.
* EBACKGROUND: (libc)Error Codes.
* EBADE: (libc)Error Codes.
* EBADF: (libc)Error Codes.
* EBADFD: (libc)Error Codes.
* EBADMSG: (libc)Error Codes.
* EBADR: (libc)Error Codes.
* EBADRPC: (libc)Error Codes.
* EBADRQC: (libc)Error Codes.
* EBADSLT: (libc)Error Codes.
* EBFONT: (libc)Error Codes.
* EBUSY: (libc)Error Codes.
* ECANCELED: (libc)Error Codes.
* ECHILD: (libc)Error Codes.
* ECHO: (libc)Local Modes.
* ECHOCTL: (libc)Local Modes.
* ECHOE: (libc)Local Modes.
* ECHOK: (libc)Local Modes.
* ECHOKE: (libc)Local Modes.
* ECHONL: (libc)Local Modes.
* ECHOPRT: (libc)Local Modes.
* ECHRNG: (libc)Error Codes.
* ECOMM: (libc)Error Codes.
* ECONNABORTED: (libc)Error Codes.
* ECONNREFUSED: (libc)Error Codes.
* ECONNRESET: (libc)Error Codes.
* ED: (libc)Error Codes.
* EDEADLK: (libc)Error Codes.
* EDEADLOCK: (libc)Error Codes.
* EDESTADDRREQ: (libc)Error Codes.
* EDIED: (libc)Error Codes.
* EDOM: (libc)Error Codes.
* EDOTDOT: (libc)Error Codes.
* EDQUOT: (libc)Error Codes.
* EEXIST: (libc)Error Codes.
* EFAULT: (libc)Error Codes.
* EFBIG: (libc)Error Codes.
* EFTYPE: (libc)Error Codes.
* EGRATUITOUS: (libc)Error Codes.
* EGREGIOUS: (libc)Error Codes.
* EHOSTDOWN: (libc)Error Codes.
* EHOSTUNREACH: (libc)Error Codes.
* EHWPOISON: (libc)Error Codes.
* EIDRM: (libc)Error Codes.
* EIEIO: (libc)Error Codes.
* EILSEQ: (libc)Error Codes.
* EINPROGRESS: (libc)Error Codes.
* EINTR: (libc)Error Codes.
* EINVAL: (libc)Error Codes.
* EIO: (libc)Error Codes.
* EISCONN: (libc)Error Codes.
* EISDIR: (libc)Error Codes.
* EISNAM: (libc)Error Codes.
* EKEYEXPIRED: (libc)Error Codes.
* EKEYREJECTED: (libc)Error Codes.
* EKEYREVOKED: (libc)Error Codes.
* EL2HLT: (libc)Error Codes.
* EL2NSYNC: (libc)Error Codes.
* EL3HLT: (libc)Error Codes.
* EL3RST: (libc)Error Codes.
* ELIBACC: (libc)Error Codes.
* ELIBBAD: (libc)Error Codes.
* ELIBEXEC: (libc)Error Codes.
* ELIBMAX: (libc)Error Codes.
* ELIBSCN: (libc)Error Codes.
* ELNRNG: (libc)Error Codes.
* ELOOP: (libc)Error Codes.
* EMEDIUMTYPE: (libc)Error Codes.
* EMFILE: (libc)Error Codes.
* EMLINK: (libc)Error Codes.
* EMSGSIZE: (libc)Error Codes.
* EMULTIHOP: (libc)Error Codes.
* ENAMETOOLONG: (libc)Error Codes.
* ENAVAIL: (libc)Error Codes.
* ENEEDAUTH: (libc)Error Codes.
* ENETDOWN: (libc)Error Codes.
* ENETRESET: (libc)Error Codes.
* ENETUNREACH: (libc)Error Codes.
* ENFILE: (libc)Error Codes.
* ENOANO: (libc)Error Codes.
* ENOBUFS: (libc)Error Codes.
* ENOCSI: (libc)Error Codes.
* ENODATA: (libc)Error Codes.
* ENODEV: (libc)Error Codes.
* ENOENT: (libc)Error Codes.
* ENOEXEC: (libc)Error Codes.
* ENOKEY: (libc)Error Codes.
* ENOLCK: (libc)Error Codes.
* ENOLINK: (libc)Error Codes.
* ENOMEDIUM: (libc)Error Codes.
* ENOMEM: (libc)Error Codes.
* ENOMSG: (libc)Error Codes.
* ENONET: (libc)Error Codes.
* ENOPKG: (libc)Error Codes.
* ENOPROTOOPT: (libc)Error Codes.
* ENOSPC: (libc)Error Codes.
* ENOSR: (libc)Error Codes.
* ENOSTR: (libc)Error Codes.
* ENOSYS: (libc)Error Codes.
* ENOTBLK: (libc)Error Codes.
* ENOTCONN: (libc)Error Codes.
* ENOTDIR: (libc)Error Codes.
* ENOTEMPTY: (libc)Error Codes.
* ENOTNAM: (libc)Error Codes.
* ENOTRECOVERABLE: (libc)Error Codes.
* ENOTSOCK: (libc)Error Codes.
* ENOTSUP: (libc)Error Codes.
* ENOTTY: (libc)Error Codes.
* ENOTUNIQ: (libc)Error Codes.
* ENXIO: (libc)Error Codes.
* EOF: (libc)EOF and Errors.
* EOPNOTSUPP: (libc)Error Codes.
* EOVERFLOW: (libc)Error Codes.
* EOWNERDEAD: (libc)Error Codes.
* EPERM: (libc)Error Codes.
* EPFNOSUPPORT: (libc)Error Codes.
* EPIPE: (libc)Error Codes.
* EPROCLIM: (libc)Error Codes.
* EPROCUNAVAIL: (libc)Error Codes.
* EPROGMISMATCH: (libc)Error Codes.
* EPROGUNAVAIL: (libc)Error Codes.
* EPROTO: (libc)Error Codes.
* EPROTONOSUPPORT: (libc)Error Codes.
* EPROTOTYPE: (libc)Error Codes.
* EQUIV_CLASS_MAX: (libc)Utility Limits.
* ERANGE: (libc)Error Codes.
* EREMCHG: (libc)Error Codes.
* EREMOTE: (libc)Error Codes.
* EREMOTEIO: (libc)Error Codes.
* ERESTART: (libc)Error Codes.
* ERFKILL: (libc)Error Codes.
* EROFS: (libc)Error Codes.
* ERPCMISMATCH: (libc)Error Codes.
* ESHUTDOWN: (libc)Error Codes.
* ESOCKTNOSUPPORT: (libc)Error Codes.
* ESPIPE: (libc)Error Codes.
* ESRCH: (libc)Error Codes.
* ESRMNT: (libc)Error Codes.
* ESTALE: (libc)Error Codes.
* ESTRPIPE: (libc)Error Codes.
* ETIME: (libc)Error Codes.
* ETIMEDOUT: (libc)Error Codes.
* ETOOMANYREFS: (libc)Error Codes.
* ETXTBSY: (libc)Error Codes.
* EUCLEAN: (libc)Error Codes.
* EUNATCH: (libc)Error Codes.
* EUSERS: (libc)Error Codes.
* EWOULDBLOCK: (libc)Error Codes.
* EXDEV: (libc)Error Codes.
* EXFULL: (libc)Error Codes.
* EXIT_FAILURE: (libc)Exit Status.
* EXIT_SUCCESS: (libc)Exit Status.
* EXPR_NEST_MAX: (libc)Utility Limits.
* FD_CLOEXEC: (libc)Descriptor Flags.
* FD_CLR: (libc)Waiting for I/O.
* FD_ISSET: (libc)Waiting for I/O.
* FD_SET: (libc)Waiting for I/O.
* FD_SETSIZE: (libc)Waiting for I/O.
* FD_ZERO: (libc)Waiting for I/O.
* FILENAME_MAX: (libc)Limits for Files.
* FLUSHO: (libc)Local Modes.
* FOPEN_MAX: (libc)Opening Streams.
* FP_ILOGB0: (libc)Exponents and Logarithms.
* FP_ILOGBNAN: (libc)Exponents and Logarithms.
* F_DUPFD: (libc)Duplicating Descriptors.
* F_GETFD: (libc)Descriptor Flags.
* F_GETFL: (libc)Getting File Status Flags.
* F_GETLK: (libc)File Locks.
* F_GETOWN: (libc)Interrupt Input.
* F_OK: (libc)Testing File Access.
* F_SETFD: (libc)Descriptor Flags.
* F_SETFL: (libc)Getting File Status Flags.
* F_SETLK: (libc)File Locks.
* F_SETLKW: (libc)File Locks.
* F_SETOWN: (libc)Interrupt Input.
* HUGE_VAL: (libc)Math Error Reporting.
* HUGE_VALF: (libc)Math Error Reporting.
* HUGE_VALL: (libc)Math Error Reporting.
* HUPCL: (libc)Control Modes.
* I: (libc)Complex Numbers.
* ICANON: (libc)Local Modes.
* ICRNL: (libc)Input Modes.
* IEXTEN: (libc)Local Modes.
* IFNAMSIZ: (libc)Interface Naming.
* IFTODT: (libc)Directory Entries.
* IGNBRK: (libc)Input Modes.
* IGNCR: (libc)Input Modes.
* IGNPAR: (libc)Input Modes.
* IMAXBEL: (libc)Input Modes.
* INADDR_ANY: (libc)Host Address Data Type.
* INADDR_BROADCAST: (libc)Host Address Data Type.
* INADDR_LOOPBACK: (libc)Host Address Data Type.
* INADDR_NONE: (libc)Host Address Data Type.
* INFINITY: (libc)Infinity and NaN.
* INLCR: (libc)Input Modes.
* INPCK: (libc)Input Modes.
* IPPORT_RESERVED: (libc)Ports.
* IPPORT_USERRESERVED: (libc)Ports.
* ISIG: (libc)Local Modes.
* ISTRIP: (libc)Input Modes.
* IXANY: (libc)Input Modes.
* IXOFF: (libc)Input Modes.
* IXON: (libc)Input Modes.
* LINE_MAX: (libc)Utility Limits.
* LINK_MAX: (libc)Limits for Files.
* L_ctermid: (libc)Identifying the Terminal.
* L_cuserid: (libc)Who Logged In.
* L_tmpnam: (libc)Temporary Files.
* MAXNAMLEN: (libc)Limits for Files.
* MAXSYMLINKS: (libc)Symbolic Links.
* MAX_CANON: (libc)Limits for Files.
* MAX_INPUT: (libc)Limits for Files.
* MB_CUR_MAX: (libc)Selecting the Conversion.
* MB_LEN_MAX: (libc)Selecting the Conversion.
* MDMBUF: (libc)Control Modes.
* MSG_DONTROUTE: (libc)Socket Data Options.
* MSG_OOB: (libc)Socket Data Options.
* MSG_PEEK: (libc)Socket Data Options.
* NAME_MAX: (libc)Limits for Files.
* NAN: (libc)Infinity and NaN.
* NCCS: (libc)Mode Data Types.
* NGROUPS_MAX: (libc)General Limits.
* NOFLSH: (libc)Local Modes.
* NOKERNINFO: (libc)Local Modes.
* NSIG: (libc)Standard Signals.
* NULL: (libc)Null Pointer Constant.
* ONLCR: (libc)Output Modes.
* ONOEOT: (libc)Output Modes.
* OPEN_MAX: (libc)General Limits.
* OPOST: (libc)Output Modes.
* OXTABS: (libc)Output Modes.
* O_ACCMODE: (libc)Access Modes.
* O_APPEND: (libc)Operating Modes.
* O_ASYNC: (libc)Operating Modes.
* O_CREAT: (libc)Open-time Flags.
* O_EXCL: (libc)Open-time Flags.
* O_EXEC: (libc)Access Modes.
* O_EXLOCK: (libc)Open-time Flags.
* O_FSYNC: (libc)Operating Modes.
* O_IGNORE_CTTY: (libc)Open-time Flags.
* O_NDELAY: (libc)Operating Modes.
* O_NOATIME: (libc)Operating Modes.
* O_NOCTTY: (libc)Open-time Flags.
* O_NOLINK: (libc)Open-time Flags.
* O_NONBLOCK: (libc)Open-time Flags.
* O_NONBLOCK: (libc)Operating Modes.
* O_NOTRANS: (libc)Open-time Flags.
* O_RDONLY: (libc)Access Modes.
* O_RDWR: (libc)Access Modes.
* O_READ: (libc)Access Modes.
* O_SHLOCK: (libc)Open-time Flags.
* O_SYNC: (libc)Operating Modes.
* O_TRUNC: (libc)Open-time Flags.
* O_WRITE: (libc)Access Modes.
* O_WRONLY: (libc)Access Modes.
* PARENB: (libc)Control Modes.
* PARMRK: (libc)Input Modes.
* PARODD: (libc)Control Modes.
* PATH_MAX: (libc)Limits for Files.
* PA_FLAG_MASK: (libc)Parsing a Template String.
* PENDIN: (libc)Local Modes.
* PF_FILE: (libc)Local Namespace Details.
* PF_INET6: (libc)Internet Namespace.
* PF_INET: (libc)Internet Namespace.
* PF_LOCAL: (libc)Local Namespace Details.
* PF_UNIX: (libc)Local Namespace Details.
* PIPE_BUF: (libc)Limits for Files.
* P_tmpdir: (libc)Temporary Files.
* RAND_MAX: (libc)ISO Random.
* RE_DUP_MAX: (libc)General Limits.
* RLIM_INFINITY: (libc)Limits on Resources.
* R_OK: (libc)Testing File Access.
* SA_NOCLDSTOP: (libc)Flags for Sigaction.
* SA_ONSTACK: (libc)Flags for Sigaction.
* SA_RESTART: (libc)Flags for Sigaction.
* SEEK_CUR: (libc)File Positioning.
* SEEK_END: (libc)File Positioning.
* SEEK_SET: (libc)File Positioning.
* SIGABRT: (libc)Program Error Signals.
* SIGALRM: (libc)Alarm Signals.
* SIGBUS: (libc)Program Error Signals.
* SIGCHLD: (libc)Job Control Signals.
* SIGCLD: (libc)Job Control Signals.
* SIGCONT: (libc)Job Control Signals.
* SIGEMT: (libc)Program Error Signals.
* SIGFPE: (libc)Program Error Signals.
* SIGHUP: (libc)Termination Signals.
* SIGILL: (libc)Program Error Signals.
* SIGINFO: (libc)Miscellaneous Signals.
* SIGINT: (libc)Termination Signals.
* SIGIO: (libc)Asynchronous I/O Signals.
* SIGIOT: (libc)Program Error Signals.
* SIGKILL: (libc)Termination Signals.
* SIGLOST: (libc)Operation Error Signals.
* SIGPIPE: (libc)Operation Error Signals.
* SIGPOLL: (libc)Asynchronous I/O Signals.
* SIGPROF: (libc)Alarm Signals.
* SIGQUIT: (libc)Termination Signals.
* SIGSEGV: (libc)Program Error Signals.
* SIGSTOP: (libc)Job Control Signals.
* SIGSYS: (libc)Program Error Signals.
* SIGTERM: (libc)Termination Signals.
* SIGTRAP: (libc)Program Error Signals.
* SIGTSTP: (libc)Job Control Signals.
* SIGTTIN: (libc)Job Control Signals.
* SIGTTOU: (libc)Job Control Signals.
* SIGURG: (libc)Asynchronous I/O Signals.
* SIGUSR1: (libc)Miscellaneous Signals.
* SIGUSR2: (libc)Miscellaneous Signals.
* SIGVTALRM: (libc)Alarm Signals.
* SIGWINCH: (libc)Miscellaneous Signals.
* SIGXCPU: (libc)Operation Error Signals.
* SIGXFSZ: (libc)Operation Error Signals.
* SIG_ERR: (libc)Basic Signal Handling.
* SOCK_DGRAM: (libc)Communication Styles.
* SOCK_RAW: (libc)Communication Styles.
* SOCK_RDM: (libc)Communication Styles.
* SOCK_SEQPACKET: (libc)Communication Styles.
* SOCK_STREAM: (libc)Communication Styles.
* SOL_SOCKET: (libc)Socket-Level Options.
* SSIZE_MAX: (libc)General Limits.
* STREAM_MAX: (libc)General Limits.
* SUN_LEN: (libc)Local Namespace Details.
* SV_INTERRUPT: (libc)BSD Handler.
* SV_ONSTACK: (libc)BSD Handler.
* SV_RESETHAND: (libc)BSD Handler.
* S_IFMT: (libc)Testing File Type.
* S_ISBLK: (libc)Testing File Type.
* S_ISCHR: (libc)Testing File Type.
* S_ISDIR: (libc)Testing File Type.
* S_ISFIFO: (libc)Testing File Type.
* S_ISLNK: (libc)Testing File Type.
* S_ISREG: (libc)Testing File Type.
* S_ISSOCK: (libc)Testing File Type.
* S_TYPEISMQ: (libc)Testing File Type.
* S_TYPEISSEM: (libc)Testing File Type.
* S_TYPEISSHM: (libc)Testing File Type.
* TMP_MAX: (libc)Temporary Files.
* TOSTOP: (libc)Local Modes.
* TZNAME_MAX: (libc)General Limits.
* VDISCARD: (libc)Other Special.
* VDSUSP: (libc)Signal Characters.
* VEOF: (libc)Editing Characters.
* VEOL2: (libc)Editing Characters.
* VEOL: (libc)Editing Characters.
* VERASE: (libc)Editing Characters.
* VINTR: (libc)Signal Characters.
* VKILL: (libc)Editing Characters.
* VLNEXT: (libc)Other Special.
* VMIN: (libc)Noncanonical Input.
* VQUIT: (libc)Signal Characters.
* VREPRINT: (libc)Editing Characters.
* VSTART: (libc)Start/Stop Characters.
* VSTATUS: (libc)Other Special.
* VSTOP: (libc)Start/Stop Characters.
* VSUSP: (libc)Signal Characters.
* VTIME: (libc)Noncanonical Input.
* VWERASE: (libc)Editing Characters.
* WCHAR_MAX: (libc)Extended Char Intro.
* WCHAR_MIN: (libc)Extended Char Intro.
* WCOREDUMP: (libc)Process Completion Status.
* WEOF: (libc)EOF and Errors.
* WEOF: (libc)Extended Char Intro.
* WEXITSTATUS: (libc)Process Completion Status.
* WIFEXITED: (libc)Process Completion Status.
* WIFSIGNALED: (libc)Process Completion Status.
* WIFSTOPPED: (libc)Process Completion Status.
* WSTOPSIG: (libc)Process Completion Status.
* WTERMSIG: (libc)Process Completion Status.
* W_OK: (libc)Testing File Access.
* X_OK: (libc)Testing File Access.
* _Complex_I: (libc)Complex Numbers.
* _Exit: (libc)Termination Internals.
* _IOFBF: (libc)Controlling Buffering.
* _IOLBF: (libc)Controlling Buffering.
* _IONBF: (libc)Controlling Buffering.
* _Imaginary_I: (libc)Complex Numbers.
* _PATH_UTMP: (libc)Manipulating the Database.
* _PATH_WTMP: (libc)Manipulating the Database.
* _POSIX2_C_DEV: (libc)System Options.
* _POSIX2_C_VERSION: (libc)Version Supported.
* _POSIX2_FORT_DEV: (libc)System Options.
* _POSIX2_FORT_RUN: (libc)System Options.
* _POSIX2_LOCALEDEF: (libc)System Options.
* _POSIX2_SW_DEV: (libc)System Options.
* _POSIX_CHOWN_RESTRICTED: (libc)Options for Files.
* _POSIX_JOB_CONTROL: (libc)System Options.
* _POSIX_NO_TRUNC: (libc)Options for Files.
* _POSIX_SAVED_IDS: (libc)System Options.
* _POSIX_VDISABLE: (libc)Options for Files.
* _POSIX_VERSION: (libc)Version Supported.
* __fbufsize: (libc)Controlling Buffering.
* __flbf: (libc)Controlling Buffering.
* __fpending: (libc)Controlling Buffering.
* __fpurge: (libc)Flushing Buffers.
* __freadable: (libc)Opening Streams.
* __freading: (libc)Opening Streams.
* __fsetlocking: (libc)Streams and Threads.
* __fwritable: (libc)Opening Streams.
* __fwriting: (libc)Opening Streams.
* __gconv_end_fct: (libc)glibc iconv Implementation.
* __gconv_fct: (libc)glibc iconv Implementation.
* __gconv_init_fct: (libc)glibc iconv Implementation.
* __ppc_get_timebase: (libc)PowerPC.
* __ppc_get_timebase_freq: (libc)PowerPC.
* __ppc_mdoio: (libc)PowerPC.
* __ppc_mdoom: (libc)PowerPC.
* __ppc_set_ppr_low: (libc)PowerPC.
* __ppc_set_ppr_med: (libc)PowerPC.
* __ppc_set_ppr_med_low: (libc)PowerPC.
* __ppc_yield: (libc)PowerPC.
* __va_copy: (libc)Argument Macros.
* _exit: (libc)Termination Internals.
* _flushlbf: (libc)Flushing Buffers.
* _tolower: (libc)Case Conversion.
* _toupper: (libc)Case Conversion.
* a64l: (libc)Encode Binary Data.
* abort: (libc)Aborting a Program.
* abs: (libc)Absolute Value.
* accept: (libc)Accepting Connections.
* access: (libc)Testing File Access.
* acos: (libc)Inverse Trig Functions.
* acosf: (libc)Inverse Trig Functions.
* acosh: (libc)Hyperbolic Functions.
* acoshf: (libc)Hyperbolic Functions.
* acoshl: (libc)Hyperbolic Functions.
* acosl: (libc)Inverse Trig Functions.
* addmntent: (libc)mtab.
* addseverity: (libc)Adding Severity Classes.
* adjtime: (libc)High-Resolution Calendar.
* adjtimex: (libc)High-Resolution Calendar.
* aio_cancel64: (libc)Cancel AIO Operations.
* aio_cancel: (libc)Cancel AIO Operations.
* aio_error64: (libc)Status of AIO Operations.
* aio_error: (libc)Status of AIO Operations.
* aio_fsync64: (libc)Synchronizing AIO Operations.
* aio_fsync: (libc)Synchronizing AIO Operations.
* aio_init: (libc)Configuration of AIO.
* aio_read64: (libc)Asynchronous Reads/Writes.
* aio_read: (libc)Asynchronous Reads/Writes.
* aio_return64: (libc)Status of AIO Operations.
* aio_return: (libc)Status of AIO Operations.
* aio_suspend64: (libc)Synchronizing AIO Operations.
* aio_suspend: (libc)Synchronizing AIO Operations.
* aio_write64: (libc)Asynchronous Reads/Writes.
* aio_write: (libc)Asynchronous Reads/Writes.
* alarm: (libc)Setting an Alarm.
* aligned_alloc: (libc)Aligned Memory Blocks.
* alloca: (libc)Variable Size Automatic.
* alphasort64: (libc)Scanning Directory Content.
* alphasort: (libc)Scanning Directory Content.
* argp_error: (libc)Argp Helper Functions.
* argp_failure: (libc)Argp Helper Functions.
* argp_help: (libc)Argp Help.
* argp_parse: (libc)Argp.
* argp_state_help: (libc)Argp Helper Functions.
* argp_usage: (libc)Argp Helper Functions.
* argz_add: (libc)Argz Functions.
* argz_add_sep: (libc)Argz Functions.
* argz_append: (libc)Argz Functions.
* argz_count: (libc)Argz Functions.
* argz_create: (libc)Argz Functions.
* argz_create_sep: (libc)Argz Functions.
* argz_delete: (libc)Argz Functions.
* argz_extract: (libc)Argz Functions.
* argz_insert: (libc)Argz Functions.
* argz_next: (libc)Argz Functions.
* argz_replace: (libc)Argz Functions.
* argz_stringify: (libc)Argz Functions.
* asctime: (libc)Formatting Calendar Time.
* asctime_r: (libc)Formatting Calendar Time.
* asin: (libc)Inverse Trig Functions.
* asinf: (libc)Inverse Trig Functions.
* asinh: (libc)Hyperbolic Functions.
* asinhf: (libc)Hyperbolic Functions.
* asinhl: (libc)Hyperbolic Functions.
* asinl: (libc)Inverse Trig Functions.
* asprintf: (libc)Dynamic Output.
* assert: (libc)Consistency Checking.
* assert_perror: (libc)Consistency Checking.
* atan2: (libc)Inverse Trig Functions.
* atan2f: (libc)Inverse Trig Functions.
* atan2l: (libc)Inverse Trig Functions.
* atan: (libc)Inverse Trig Functions.
* atanf: (libc)Inverse Trig Functions.
* atanh: (libc)Hyperbolic Functions.
* atanhf: (libc)Hyperbolic Functions.
* atanhl: (libc)Hyperbolic Functions.
* atanl: (libc)Inverse Trig Functions.
* atexit: (libc)Cleanups on Exit.
* atof: (libc)Parsing of Floats.
* atoi: (libc)Parsing of Integers.
* atol: (libc)Parsing of Integers.
* atoll: (libc)Parsing of Integers.
* backtrace: (libc)Backtraces.
* backtrace_symbols: (libc)Backtraces.
* backtrace_symbols_fd: (libc)Backtraces.
* basename: (libc)Finding Tokens in a String.
* basename: (libc)Finding Tokens in a String.
* bcmp: (libc)String/Array Comparison.
* bcopy: (libc)Copying and Concatenation.
* bind: (libc)Setting Address.
* bind_textdomain_codeset: (libc)Charset conversion in gettext.
* bindtextdomain: (libc)Locating gettext catalog.
* brk: (libc)Resizing the Data Segment.
* bsearch: (libc)Array Search Function.
* btowc: (libc)Converting a Character.
* bzero: (libc)Copying and Concatenation.
* cabs: (libc)Absolute Value.
* cabsf: (libc)Absolute Value.
* cabsl: (libc)Absolute Value.
* cacos: (libc)Inverse Trig Functions.
* cacosf: (libc)Inverse Trig Functions.
* cacosh: (libc)Hyperbolic Functions.
* cacoshf: (libc)Hyperbolic Functions.
* cacoshl: (libc)Hyperbolic Functions.
* cacosl: (libc)Inverse Trig Functions.
* calloc: (libc)Allocating Cleared Space.
* canonicalize_file_name: (libc)Symbolic Links.
* carg: (libc)Operations on Complex.
* cargf: (libc)Operations on Complex.
* cargl: (libc)Operations on Complex.
* casin: (libc)Inverse Trig Functions.
* casinf: (libc)Inverse Trig Functions.
* casinh: (libc)Hyperbolic Functions.
* casinhf: (libc)Hyperbolic Functions.
* casinhl: (libc)Hyperbolic Functions.
* casinl: (libc)Inverse Trig Functions.
* catan: (libc)Inverse Trig Functions.
* catanf: (libc)Inverse Trig Functions.
* catanh: (libc)Hyperbolic Functions.
* catanhf: (libc)Hyperbolic Functions.
* catanhl: (libc)Hyperbolic Functions.
* catanl: (libc)Inverse Trig Functions.
* catclose: (libc)The catgets Functions.
* catgets: (libc)The catgets Functions.
* catopen: (libc)The catgets Functions.
* cbc_crypt: (libc)DES Encryption.
* cbrt: (libc)Exponents and Logarithms.
* cbrtf: (libc)Exponents and Logarithms.
* cbrtl: (libc)Exponents and Logarithms.
* ccos: (libc)Trig Functions.
* ccosf: (libc)Trig Functions.
* ccosh: (libc)Hyperbolic Functions.
* ccoshf: (libc)Hyperbolic Functions.
* ccoshl: (libc)Hyperbolic Functions.
* ccosl: (libc)Trig Functions.
* ceil: (libc)Rounding Functions.
* ceilf: (libc)Rounding Functions.
* ceill: (libc)Rounding Functions.
* cexp: (libc)Exponents and Logarithms.
* cexpf: (libc)Exponents and Logarithms.
* cexpl: (libc)Exponents and Logarithms.
* cfgetispeed: (libc)Line Speed.
* cfgetospeed: (libc)Line Speed.
* cfmakeraw: (libc)Noncanonical Input.
* cfree: (libc)Freeing after Malloc.
* cfsetispeed: (libc)Line Speed.
* cfsetospeed: (libc)Line Speed.
* cfsetspeed: (libc)Line Speed.
* chdir: (libc)Working Directory.
* chmod: (libc)Setting Permissions.
* chown: (libc)File Owner.
* cimag: (libc)Operations on Complex.
* cimagf: (libc)Operations on Complex.
* cimagl: (libc)Operations on Complex.
* clearenv: (libc)Environment Access.
* clearerr: (libc)Error Recovery.
* clearerr_unlocked: (libc)Error Recovery.
* clock: (libc)CPU Time.
* clog10: (libc)Exponents and Logarithms.
* clog10f: (libc)Exponents and Logarithms.
* clog10l: (libc)Exponents and Logarithms.
* clog: (libc)Exponents and Logarithms.
* clogf: (libc)Exponents and Logarithms.
* clogl: (libc)Exponents and Logarithms.
* close: (libc)Opening and Closing Files.
* closedir: (libc)Reading/Closing Directory.
* closelog: (libc)closelog.
* confstr: (libc)String Parameters.
* conj: (libc)Operations on Complex.
* conjf: (libc)Operations on Complex.
* conjl: (libc)Operations on Complex.
* connect: (libc)Connecting.
* copysign: (libc)FP Bit Twiddling.
* copysignf: (libc)FP Bit Twiddling.
* copysignl: (libc)FP Bit Twiddling.
* cos: (libc)Trig Functions.
* cosf: (libc)Trig Functions.
* cosh: (libc)Hyperbolic Functions.
* coshf: (libc)Hyperbolic Functions.
* coshl: (libc)Hyperbolic Functions.
* cosl: (libc)Trig Functions.
* cpow: (libc)Exponents and Logarithms.
* cpowf: (libc)Exponents and Logarithms.
* cpowl: (libc)Exponents and Logarithms.
* cproj: (libc)Operations on Complex.
* cprojf: (libc)Operations on Complex.
* cprojl: (libc)Operations on Complex.
* creal: (libc)Operations on Complex.
* crealf: (libc)Operations on Complex.
* creall: (libc)Operations on Complex.
* creat64: (libc)Opening and Closing Files.
* creat: (libc)Opening and Closing Files.
* crypt: (libc)crypt.
* crypt_r: (libc)crypt.
* csin: (libc)Trig Functions.
* csinf: (libc)Trig Functions.
* csinh: (libc)Hyperbolic Functions.
* csinhf: (libc)Hyperbolic Functions.
* csinhl: (libc)Hyperbolic Functions.
* csinl: (libc)Trig Functions.
* csqrt: (libc)Exponents and Logarithms.
* csqrtf: (libc)Exponents and Logarithms.
* csqrtl: (libc)Exponents and Logarithms.
* ctan: (libc)Trig Functions.
* ctanf: (libc)Trig Functions.
* ctanh: (libc)Hyperbolic Functions.
* ctanhf: (libc)Hyperbolic Functions.
* ctanhl: (libc)Hyperbolic Functions.
* ctanl: (libc)Trig Functions.
* ctermid: (libc)Identifying the Terminal.
* ctime: (libc)Formatting Calendar Time.
* ctime_r: (libc)Formatting Calendar Time.
* cuserid: (libc)Who Logged In.
* dcgettext: (libc)Translation with gettext.
* dcngettext: (libc)Advanced gettext functions.
* des_setparity: (libc)DES Encryption.
* dgettext: (libc)Translation with gettext.
* difftime: (libc)Elapsed Time.
* dirfd: (libc)Opening a Directory.
* dirname: (libc)Finding Tokens in a String.
* div: (libc)Integer Division.
* dngettext: (libc)Advanced gettext functions.
* drand48: (libc)SVID Random.
* drand48_r: (libc)SVID Random.
* drem: (libc)Remainder Functions.
* dremf: (libc)Remainder Functions.
* dreml: (libc)Remainder Functions.
* dup2: (libc)Duplicating Descriptors.
* dup: (libc)Duplicating Descriptors.
* ecb_crypt: (libc)DES Encryption.
* ecvt: (libc)System V Number Conversion.
* ecvt_r: (libc)System V Number Conversion.
* encrypt: (libc)DES Encryption.
* encrypt_r: (libc)DES Encryption.
* endfsent: (libc)fstab.
* endgrent: (libc)Scanning All Groups.
* endhostent: (libc)Host Names.
* endmntent: (libc)mtab.
* endnetent: (libc)Networks Database.
* endnetgrent: (libc)Lookup Netgroup.
* endprotoent: (libc)Protocols Database.
* endpwent: (libc)Scanning All Users.
* endservent: (libc)Services Database.
* endutent: (libc)Manipulating the Database.
* endutxent: (libc)XPG Functions.
* envz_add: (libc)Envz Functions.
* envz_entry: (libc)Envz Functions.
* envz_get: (libc)Envz Functions.
* envz_merge: (libc)Envz Functions.
* envz_strip: (libc)Envz Functions.
* erand48: (libc)SVID Random.
* erand48_r: (libc)SVID Random.
* erf: (libc)Special Functions.
* erfc: (libc)Special Functions.
* erfcf: (libc)Special Functions.
* erfcl: (libc)Special Functions.
* erff: (libc)Special Functions.
* erfl: (libc)Special Functions.
* err: (libc)Error Messages.
* errno: (libc)Checking for Errors.
* error: (libc)Error Messages.
* error_at_line: (libc)Error Messages.
* errx: (libc)Error Messages.
* execl: (libc)Executing a File.
* execle: (libc)Executing a File.
* execlp: (libc)Executing a File.
* execv: (libc)Executing a File.
* execve: (libc)Executing a File.
* execvp: (libc)Executing a File.
* exit: (libc)Normal Termination.
* exp10: (libc)Exponents and Logarithms.
* exp10f: (libc)Exponents and Logarithms.
* exp10l: (libc)Exponents and Logarithms.
* exp2: (libc)Exponents and Logarithms.
* exp2f: (libc)Exponents and Logarithms.
* exp2l: (libc)Exponents and Logarithms.
* exp: (libc)Exponents and Logarithms.
* expf: (libc)Exponents and Logarithms.
* expl: (libc)Exponents and Logarithms.
* expm1: (libc)Exponents and Logarithms.
* expm1f: (libc)Exponents and Logarithms.
* expm1l: (libc)Exponents and Logarithms.
* fabs: (libc)Absolute Value.
* fabsf: (libc)Absolute Value.
* fabsl: (libc)Absolute Value.
* fchdir: (libc)Working Directory.
* fchmod: (libc)Setting Permissions.
* fchown: (libc)File Owner.
* fclose: (libc)Closing Streams.
* fcloseall: (libc)Closing Streams.
* fcntl: (libc)Control Operations.
* fcvt: (libc)System V Number Conversion.
* fcvt_r: (libc)System V Number Conversion.
* fdatasync: (libc)Synchronizing I/O.
* fdim: (libc)Misc FP Arithmetic.
* fdimf: (libc)Misc FP Arithmetic.
* fdiml: (libc)Misc FP Arithmetic.
* fdopen: (libc)Descriptors and Streams.
* fdopendir: (libc)Opening a Directory.
* feclearexcept: (libc)Status bit operations.
* fedisableexcept: (libc)Control Functions.
* feenableexcept: (libc)Control Functions.
* fegetenv: (libc)Control Functions.
* fegetexcept: (libc)Control Functions.
* fegetexceptflag: (libc)Status bit operations.
* fegetround: (libc)Rounding.
* feholdexcept: (libc)Control Functions.
* feof: (libc)EOF and Errors.
* feof_unlocked: (libc)EOF and Errors.
* feraiseexcept: (libc)Status bit operations.
* ferror: (libc)EOF and Errors.
* ferror_unlocked: (libc)EOF and Errors.
* fesetenv: (libc)Control Functions.
* fesetexceptflag: (libc)Status bit operations.
* fesetround: (libc)Rounding.
* fetestexcept: (libc)Status bit operations.
* feupdateenv: (libc)Control Functions.
* fflush: (libc)Flushing Buffers.
* fflush_unlocked: (libc)Flushing Buffers.
* fgetc: (libc)Character Input.
* fgetc_unlocked: (libc)Character Input.
* fgetgrent: (libc)Scanning All Groups.
* fgetgrent_r: (libc)Scanning All Groups.
* fgetpos64: (libc)Portable Positioning.
* fgetpos: (libc)Portable Positioning.
* fgetpwent: (libc)Scanning All Users.
* fgetpwent_r: (libc)Scanning All Users.
* fgets: (libc)Line Input.
* fgets_unlocked: (libc)Line Input.
* fgetwc: (libc)Character Input.
* fgetwc_unlocked: (libc)Character Input.
* fgetws: (libc)Line Input.
* fgetws_unlocked: (libc)Line Input.
* fileno: (libc)Descriptors and Streams.
* fileno_unlocked: (libc)Descriptors and Streams.
* finite: (libc)Floating Point Classes.
* finitef: (libc)Floating Point Classes.
* finitel: (libc)Floating Point Classes.
* flockfile: (libc)Streams and Threads.
* floor: (libc)Rounding Functions.
* floorf: (libc)Rounding Functions.
* floorl: (libc)Rounding Functions.
* fma: (libc)Misc FP Arithmetic.
* fmaf: (libc)Misc FP Arithmetic.
* fmal: (libc)Misc FP Arithmetic.
* fmax: (libc)Misc FP Arithmetic.
* fmaxf: (libc)Misc FP Arithmetic.
* fmaxl: (libc)Misc FP Arithmetic.
* fmemopen: (libc)String Streams.
* fmin: (libc)Misc FP Arithmetic.
* fminf: (libc)Misc FP Arithmetic.
* fminl: (libc)Misc FP Arithmetic.
* fmod: (libc)Remainder Functions.
* fmodf: (libc)Remainder Functions.
* fmodl: (libc)Remainder Functions.
* fmtmsg: (libc)Printing Formatted Messages.
* fnmatch: (libc)Wildcard Matching.
* fopen64: (libc)Opening Streams.
* fopen: (libc)Opening Streams.
* fopencookie: (libc)Streams and Cookies.
* fork: (libc)Creating a Process.
* forkpty: (libc)Pseudo-Terminal Pairs.
* fpathconf: (libc)Pathconf.
* fpclassify: (libc)Floating Point Classes.
* fprintf: (libc)Formatted Output Functions.
* fputc: (libc)Simple Output.
* fputc_unlocked: (libc)Simple Output.
* fputs: (libc)Simple Output.
* fputs_unlocked: (libc)Simple Output.
* fputwc: (libc)Simple Output.
* fputwc_unlocked: (libc)Simple Output.
* fputws: (libc)Simple Output.
* fputws_unlocked: (libc)Simple Output.
* fread: (libc)Block Input/Output.
* fread_unlocked: (libc)Block Input/Output.
* free: (libc)Freeing after Malloc.
* freopen64: (libc)Opening Streams.
* freopen: (libc)Opening Streams.
* frexp: (libc)Normalization Functions.
* frexpf: (libc)Normalization Functions.
* frexpl: (libc)Normalization Functions.
* fscanf: (libc)Formatted Input Functions.
* fseek: (libc)File Positioning.
* fseeko64: (libc)File Positioning.
* fseeko: (libc)File Positioning.
* fsetpos64: (libc)Portable Positioning.
* fsetpos: (libc)Portable Positioning.
* fstat64: (libc)Reading Attributes.
* fstat: (libc)Reading Attributes.
* fsync: (libc)Synchronizing I/O.
* ftell: (libc)File Positioning.
* ftello64: (libc)File Positioning.
* ftello: (libc)File Positioning.
* ftruncate64: (libc)File Size.
* ftruncate: (libc)File Size.
* ftrylockfile: (libc)Streams and Threads.
* ftw64: (libc)Working with Directory Trees.
* ftw: (libc)Working with Directory Trees.
* funlockfile: (libc)Streams and Threads.
* futimes: (libc)File Times.
* fwide: (libc)Streams and I18N.
* fwprintf: (libc)Formatted Output Functions.
* fwrite: (libc)Block Input/Output.
* fwrite_unlocked: (libc)Block Input/Output.
* fwscanf: (libc)Formatted Input Functions.
* gamma: (libc)Special Functions.
* gammaf: (libc)Special Functions.
* gammal: (libc)Special Functions.
* gcvt: (libc)System V Number Conversion.
* get_avphys_pages: (libc)Query Memory Parameters.
* get_current_dir_name: (libc)Working Directory.
* get_nprocs: (libc)Processor Resources.
* get_nprocs_conf: (libc)Processor Resources.
* get_phys_pages: (libc)Query Memory Parameters.
* getauxval: (libc)Auxiliary Vector.
* getc: (libc)Character Input.
* getc_unlocked: (libc)Character Input.
* getchar: (libc)Character Input.
* getchar_unlocked: (libc)Character Input.
* getcontext: (libc)System V contexts.
* getcwd: (libc)Working Directory.
* getdate: (libc)General Time String Parsing.
* getdate_r: (libc)General Time String Parsing.
* getdelim: (libc)Line Input.
* getdomainnname: (libc)Host Identification.
* getegid: (libc)Reading Persona.
* getenv: (libc)Environment Access.
* geteuid: (libc)Reading Persona.
* getfsent: (libc)fstab.
* getfsfile: (libc)fstab.
* getfsspec: (libc)fstab.
* getgid: (libc)Reading Persona.
* getgrent: (libc)Scanning All Groups.
* getgrent_r: (libc)Scanning All Groups.
* getgrgid: (libc)Lookup Group.
* getgrgid_r: (libc)Lookup Group.
* getgrnam: (libc)Lookup Group.
* getgrnam_r: (libc)Lookup Group.
* getgrouplist: (libc)Setting Groups.
* getgroups: (libc)Reading Persona.
* gethostbyaddr: (libc)Host Names.
* gethostbyaddr_r: (libc)Host Names.
* gethostbyname2: (libc)Host Names.
* gethostbyname2_r: (libc)Host Names.
* gethostbyname: (libc)Host Names.
* gethostbyname_r: (libc)Host Names.
* gethostent: (libc)Host Names.
* gethostid: (libc)Host Identification.
* gethostname: (libc)Host Identification.
* getitimer: (libc)Setting an Alarm.
* getline: (libc)Line Input.
* getloadavg: (libc)Processor Resources.
* getlogin: (libc)Who Logged In.
* getmntent: (libc)mtab.
* getmntent_r: (libc)mtab.
* getnetbyaddr: (libc)Networks Database.
* getnetbyname: (libc)Networks Database.
* getnetent: (libc)Networks Database.
* getnetgrent: (libc)Lookup Netgroup.
* getnetgrent_r: (libc)Lookup Netgroup.
* getopt: (libc)Using Getopt.
* getopt_long: (libc)Getopt Long Options.
* getopt_long_only: (libc)Getopt Long Options.
* getpagesize: (libc)Query Memory Parameters.
* getpass: (libc)getpass.
* getpeername: (libc)Who is Connected.
* getpgid: (libc)Process Group Functions.
* getpgrp: (libc)Process Group Functions.
* getpid: (libc)Process Identification.
* getppid: (libc)Process Identification.
* getpriority: (libc)Traditional Scheduling Functions.
* getprotobyname: (libc)Protocols Database.
* getprotobynumber: (libc)Protocols Database.
* getprotoent: (libc)Protocols Database.
* getpt: (libc)Allocation.
* getpwent: (libc)Scanning All Users.
* getpwent_r: (libc)Scanning All Users.
* getpwnam: (libc)Lookup User.
* getpwnam_r: (libc)Lookup User.
* getpwuid: (libc)Lookup User.
* getpwuid_r: (libc)Lookup User.
* getrlimit64: (libc)Limits on Resources.
* getrlimit: (libc)Limits on Resources.
* getrusage: (libc)Resource Usage.
* gets: (libc)Line Input.
* getservbyname: (libc)Services Database.
* getservbyport: (libc)Services Database.
* getservent: (libc)Services Database.
* getsid: (libc)Process Group Functions.
* getsockname: (libc)Reading Address.
* getsockopt: (libc)Socket Option Functions.
* getsubopt: (libc)Suboptions.
* gettext: (libc)Translation with gettext.
* gettimeofday: (libc)High-Resolution Calendar.
* getuid: (libc)Reading Persona.
* getumask: (libc)Setting Permissions.
* getutent: (libc)Manipulating the Database.
* getutent_r: (libc)Manipulating the Database.
* getutid: (libc)Manipulating the Database.
* getutid_r: (libc)Manipulating the Database.
* getutline: (libc)Manipulating the Database.
* getutline_r: (libc)Manipulating the Database.
* getutmp: (libc)XPG Functions.
* getutmpx: (libc)XPG Functions.
* getutxent: (libc)XPG Functions.
* getutxid: (libc)XPG Functions.
* getutxline: (libc)XPG Functions.
* getw: (libc)Character Input.
* getwc: (libc)Character Input.
* getwc_unlocked: (libc)Character Input.
* getwchar: (libc)Character Input.
* getwchar_unlocked: (libc)Character Input.
* getwd: (libc)Working Directory.
* glob64: (libc)Calling Glob.
* glob: (libc)Calling Glob.
* globfree64: (libc)More Flags for Globbing.
* globfree: (libc)More Flags for Globbing.
* gmtime: (libc)Broken-down Time.
* gmtime_r: (libc)Broken-down Time.
* grantpt: (libc)Allocation.
* gsignal: (libc)Signaling Yourself.
* gtty: (libc)BSD Terminal Modes.
* hasmntopt: (libc)mtab.
* hcreate: (libc)Hash Search Function.
* hcreate_r: (libc)Hash Search Function.
* hdestroy: (libc)Hash Search Function.
* hdestroy_r: (libc)Hash Search Function.
* hsearch: (libc)Hash Search Function.
* hsearch_r: (libc)Hash Search Function.
* htonl: (libc)Byte Order.
* htons: (libc)Byte Order.
* hypot: (libc)Exponents and Logarithms.
* hypotf: (libc)Exponents and Logarithms.
* hypotl: (libc)Exponents and Logarithms.
* iconv: (libc)Generic Conversion Interface.
* iconv_close: (libc)Generic Conversion Interface.
* iconv_open: (libc)Generic Conversion Interface.
* if_freenameindex: (libc)Interface Naming.
* if_indextoname: (libc)Interface Naming.
* if_nameindex: (libc)Interface Naming.
* if_nametoindex: (libc)Interface Naming.
* ilogb: (libc)Exponents and Logarithms.
* ilogbf: (libc)Exponents and Logarithms.
* ilogbl: (libc)Exponents and Logarithms.
* imaxabs: (libc)Absolute Value.
* imaxdiv: (libc)Integer Division.
* in6addr_any: (libc)Host Address Data Type.
* in6addr_loopback: (libc)Host Address Data Type.
* index: (libc)Search Functions.
* inet_addr: (libc)Host Address Functions.
* inet_aton: (libc)Host Address Functions.
* inet_lnaof: (libc)Host Address Functions.
* inet_makeaddr: (libc)Host Address Functions.
* inet_netof: (libc)Host Address Functions.
* inet_network: (libc)Host Address Functions.
* inet_ntoa: (libc)Host Address Functions.
* inet_ntop: (libc)Host Address Functions.
* inet_pton: (libc)Host Address Functions.
* initgroups: (libc)Setting Groups.
* initstate: (libc)BSD Random.
* initstate_r: (libc)BSD Random.
* innetgr: (libc)Netgroup Membership.
* ioctl: (libc)IOCTLs.
* isalnum: (libc)Classification of Characters.
* isalpha: (libc)Classification of Characters.
* isascii: (libc)Classification of Characters.
* isatty: (libc)Is It a Terminal.
* isblank: (libc)Classification of Characters.
* iscntrl: (libc)Classification of Characters.
* isdigit: (libc)Classification of Characters.
* isfinite: (libc)Floating Point Classes.
* isgraph: (libc)Classification of Characters.
* isgreater: (libc)FP Comparison Functions.
* isgreaterequal: (libc)FP Comparison Functions.
* isinf: (libc)Floating Point Classes.
* isinff: (libc)Floating Point Classes.
* isinfl: (libc)Floating Point Classes.
* isless: (libc)FP Comparison Functions.
* islessequal: (libc)FP Comparison Functions.
* islessgreater: (libc)FP Comparison Functions.
* islower: (libc)Classification of Characters.
* isnan: (libc)Floating Point Classes.
* isnan: (libc)Floating Point Classes.
* isnanf: (libc)Floating Point Classes.
* isnanl: (libc)Floating Point Classes.
* isnormal: (libc)Floating Point Classes.
* isprint: (libc)Classification of Characters.
* ispunct: (libc)Classification of Characters.
* issignaling: (libc)Floating Point Classes.
* isspace: (libc)Classification of Characters.
* isunordered: (libc)FP Comparison Functions.
* isupper: (libc)Classification of Characters.
* iswalnum: (libc)Classification of Wide Characters.
* iswalpha: (libc)Classification of Wide Characters.
* iswblank: (libc)Classification of Wide Characters.
* iswcntrl: (libc)Classification of Wide Characters.
* iswctype: (libc)Classification of Wide Characters.
* iswdigit: (libc)Classification of Wide Characters.
* iswgraph: (libc)Classification of Wide Characters.
* iswlower: (libc)Classification of Wide Characters.
* iswprint: (libc)Classification of Wide Characters.
* iswpunct: (libc)Classification of Wide Characters.
* iswspace: (libc)Classification of Wide Characters.
* iswupper: (libc)Classification of Wide Characters.
* iswxdigit: (libc)Classification of Wide Characters.
* isxdigit: (libc)Classification of Characters.
* j0: (libc)Special Functions.
* j0f: (libc)Special Functions.
* j0l: (libc)Special Functions.
* j1: (libc)Special Functions.
* j1f: (libc)Special Functions.
* j1l: (libc)Special Functions.
* jn: (libc)Special Functions.
* jnf: (libc)Special Functions.
* jnl: (libc)Special Functions.
* jrand48: (libc)SVID Random.
* jrand48_r: (libc)SVID Random.
* kill: (libc)Signaling Another Process.
* killpg: (libc)Signaling Another Process.
* l64a: (libc)Encode Binary Data.
* labs: (libc)Absolute Value.
* lcong48: (libc)SVID Random.
* lcong48_r: (libc)SVID Random.
* ldexp: (libc)Normalization Functions.
* ldexpf: (libc)Normalization Functions.
* ldexpl: (libc)Normalization Functions.
* ldiv: (libc)Integer Division.
* lfind: (libc)Array Search Function.
* lgamma: (libc)Special Functions.
* lgamma_r: (libc)Special Functions.
* lgammaf: (libc)Special Functions.
* lgammaf_r: (libc)Special Functions.
* lgammal: (libc)Special Functions.
* lgammal_r: (libc)Special Functions.
* link: (libc)Hard Links.
* lio_listio64: (libc)Asynchronous Reads/Writes.
* lio_listio: (libc)Asynchronous Reads/Writes.
* listen: (libc)Listening.
* llabs: (libc)Absolute Value.
* lldiv: (libc)Integer Division.
* llrint: (libc)Rounding Functions.
* llrintf: (libc)Rounding Functions.
* llrintl: (libc)Rounding Functions.
* llround: (libc)Rounding Functions.
* llroundf: (libc)Rounding Functions.
* llroundl: (libc)Rounding Functions.
* localeconv: (libc)The Lame Way to Locale Data.
* localtime: (libc)Broken-down Time.
* localtime_r: (libc)Broken-down Time.
* log10: (libc)Exponents and Logarithms.
* log10f: (libc)Exponents and Logarithms.
* log10l: (libc)Exponents and Logarithms.
* log1p: (libc)Exponents and Logarithms.
* log1pf: (libc)Exponents and Logarithms.
* log1pl: (libc)Exponents and Logarithms.
* log2: (libc)Exponents and Logarithms.
* log2f: (libc)Exponents and Logarithms.
* log2l: (libc)Exponents and Logarithms.
* log: (libc)Exponents and Logarithms.
* logb: (libc)Exponents and Logarithms.
* logbf: (libc)Exponents and Logarithms.
* logbl: (libc)Exponents and Logarithms.
* logf: (libc)Exponents and Logarithms.
* login: (libc)Logging In and Out.
* login_tty: (libc)Logging In and Out.
* logl: (libc)Exponents and Logarithms.
* logout: (libc)Logging In and Out.
* logwtmp: (libc)Logging In and Out.
* longjmp: (libc)Non-Local Details.
* lrand48: (libc)SVID Random.
* lrand48_r: (libc)SVID Random.
* lrint: (libc)Rounding Functions.
* lrintf: (libc)Rounding Functions.
* lrintl: (libc)Rounding Functions.
* lround: (libc)Rounding Functions.
* lroundf: (libc)Rounding Functions.
* lroundl: (libc)Rounding Functions.
* lsearch: (libc)Array Search Function.
* lseek64: (libc)File Position Primitive.
* lseek: (libc)File Position Primitive.
* lstat64: (libc)Reading Attributes.
* lstat: (libc)Reading Attributes.
* lutimes: (libc)File Times.
* madvise: (libc)Memory-mapped I/O.
* makecontext: (libc)System V contexts.
* mallinfo: (libc)Statistics of Malloc.
* malloc: (libc)Basic Allocation.
* mallopt: (libc)Malloc Tunable Parameters.
* mblen: (libc)Non-reentrant Character Conversion.
* mbrlen: (libc)Converting a Character.
* mbrtowc: (libc)Converting a Character.
* mbsinit: (libc)Keeping the state.
* mbsnrtowcs: (libc)Converting Strings.
* mbsrtowcs: (libc)Converting Strings.
* mbstowcs: (libc)Non-reentrant String Conversion.
* mbtowc: (libc)Non-reentrant Character Conversion.
* mcheck: (libc)Heap Consistency Checking.
* memalign: (libc)Aligned Memory Blocks.
* memccpy: (libc)Copying and Concatenation.
* memchr: (libc)Search Functions.
* memcmp: (libc)String/Array Comparison.
* memcpy: (libc)Copying and Concatenation.
* memfrob: (libc)Trivial Encryption.
* memmem: (libc)Search Functions.
* memmove: (libc)Copying and Concatenation.
* mempcpy: (libc)Copying and Concatenation.
* memrchr: (libc)Search Functions.
* memset: (libc)Copying and Concatenation.
* mkdir: (libc)Creating Directories.
* mkdtemp: (libc)Temporary Files.
* mkfifo: (libc)FIFO Special Files.
* mknod: (libc)Making Special Files.
* mkstemp: (libc)Temporary Files.
* mktemp: (libc)Temporary Files.
* mktime: (libc)Broken-down Time.
* mlock: (libc)Page Lock Functions.
* mlockall: (libc)Page Lock Functions.
* mmap64: (libc)Memory-mapped I/O.
* mmap: (libc)Memory-mapped I/O.
* modf: (libc)Rounding Functions.
* modff: (libc)Rounding Functions.
* modfl: (libc)Rounding Functions.
* mount: (libc)Mount-Unmount-Remount.
* mprobe: (libc)Heap Consistency Checking.
* mrand48: (libc)SVID Random.
* mrand48_r: (libc)SVID Random.
* mremap: (libc)Memory-mapped I/O.
* msync: (libc)Memory-mapped I/O.
* mtrace: (libc)Tracing malloc.
* munlock: (libc)Page Lock Functions.
* munlockall: (libc)Page Lock Functions.
* munmap: (libc)Memory-mapped I/O.
* muntrace: (libc)Tracing malloc.
* nan: (libc)FP Bit Twiddling.
* nanf: (libc)FP Bit Twiddling.
* nanl: (libc)FP Bit Twiddling.
* nanosleep: (libc)Sleeping.
* nearbyint: (libc)Rounding Functions.
* nearbyintf: (libc)Rounding Functions.
* nearbyintl: (libc)Rounding Functions.
* nextafter: (libc)FP Bit Twiddling.
* nextafterf: (libc)FP Bit Twiddling.
* nextafterl: (libc)FP Bit Twiddling.
* nexttoward: (libc)FP Bit Twiddling.
* nexttowardf: (libc)FP Bit Twiddling.
* nexttowardl: (libc)FP Bit Twiddling.
* nftw64: (libc)Working with Directory Trees.
* nftw: (libc)Working with Directory Trees.
* ngettext: (libc)Advanced gettext functions.
* nice: (libc)Traditional Scheduling Functions.
* nl_langinfo: (libc)The Elegant and Fast Way.
* nrand48: (libc)SVID Random.
* nrand48_r: (libc)SVID Random.
* ntohl: (libc)Byte Order.
* ntohs: (libc)Byte Order.
* ntp_adjtime: (libc)High Accuracy Clock.
* ntp_gettime: (libc)High Accuracy Clock.
* obstack_1grow: (libc)Growing Objects.
* obstack_1grow_fast: (libc)Extra Fast Growing.
* obstack_alignment_mask: (libc)Obstacks Data Alignment.
* obstack_alloc: (libc)Allocation in an Obstack.
* obstack_base: (libc)Status of an Obstack.
* obstack_blank: (libc)Growing Objects.
* obstack_blank_fast: (libc)Extra Fast Growing.
* obstack_chunk_size: (libc)Obstack Chunks.
* obstack_copy0: (libc)Allocation in an Obstack.
* obstack_copy: (libc)Allocation in an Obstack.
* obstack_finish: (libc)Growing Objects.
* obstack_free: (libc)Freeing Obstack Objects.
* obstack_grow0: (libc)Growing Objects.
* obstack_grow: (libc)Growing Objects.
* obstack_init: (libc)Preparing for Obstacks.
* obstack_int_grow: (libc)Growing Objects.
* obstack_int_grow_fast: (libc)Extra Fast Growing.
* obstack_next_free: (libc)Status of an Obstack.
* obstack_object_size: (libc)Growing Objects.
* obstack_object_size: (libc)Status of an Obstack.
* obstack_printf: (libc)Dynamic Output.
* obstack_ptr_grow: (libc)Growing Objects.
* obstack_ptr_grow_fast: (libc)Extra Fast Growing.
* obstack_room: (libc)Extra Fast Growing.
* obstack_vprintf: (libc)Variable Arguments Output.
* offsetof: (libc)Structure Measurement.
* on_exit: (libc)Cleanups on Exit.
* open64: (libc)Opening and Closing Files.
* open: (libc)Opening and Closing Files.
* open_memstream: (libc)String Streams.
* opendir: (libc)Opening a Directory.
* openlog: (libc)openlog.
* openpty: (libc)Pseudo-Terminal Pairs.
* parse_printf_format: (libc)Parsing a Template String.
* pathconf: (libc)Pathconf.
* pause: (libc)Using Pause.
* pclose: (libc)Pipe to a Subprocess.
* perror: (libc)Error Messages.
* pipe: (libc)Creating a Pipe.
* popen: (libc)Pipe to a Subprocess.
* posix_memalign: (libc)Aligned Memory Blocks.
* pow10: (libc)Exponents and Logarithms.
* pow10f: (libc)Exponents and Logarithms.
* pow10l: (libc)Exponents and Logarithms.
* pow: (libc)Exponents and Logarithms.
* powf: (libc)Exponents and Logarithms.
* powl: (libc)Exponents and Logarithms.
* pread64: (libc)I/O Primitives.
* pread: (libc)I/O Primitives.
* printf: (libc)Formatted Output Functions.
* printf_size: (libc)Predefined Printf Handlers.
* printf_size_info: (libc)Predefined Printf Handlers.
* psignal: (libc)Signal Messages.
* pthread_getattr_default_np: (libc)Default Thread Attributes.
* pthread_getspecific: (libc)Thread-specific Data.
* pthread_key_create: (libc)Thread-specific Data.
* pthread_key_delete: (libc)Thread-specific Data.
* pthread_setattr_default_np: (libc)Default Thread Attributes.
* pthread_setspecific: (libc)Thread-specific Data.
* ptsname: (libc)Allocation.
* ptsname_r: (libc)Allocation.
* putc: (libc)Simple Output.
* putc_unlocked: (libc)Simple Output.
* putchar: (libc)Simple Output.
* putchar_unlocked: (libc)Simple Output.
* putenv: (libc)Environment Access.
* putpwent: (libc)Writing a User Entry.
* puts: (libc)Simple Output.
* pututline: (libc)Manipulating the Database.
* pututxline: (libc)XPG Functions.
* putw: (libc)Simple Output.
* putwc: (libc)Simple Output.
* putwc_unlocked: (libc)Simple Output.
* putwchar: (libc)Simple Output.
* putwchar_unlocked: (libc)Simple Output.
* pwrite64: (libc)I/O Primitives.
* pwrite: (libc)I/O Primitives.
* qecvt: (libc)System V Number Conversion.
* qecvt_r: (libc)System V Number Conversion.
* qfcvt: (libc)System V Number Conversion.
* qfcvt_r: (libc)System V Number Conversion.
* qgcvt: (libc)System V Number Conversion.
* qsort: (libc)Array Sort Function.
* raise: (libc)Signaling Yourself.
* rand: (libc)ISO Random.
* rand_r: (libc)ISO Random.
* random: (libc)BSD Random.
* random_r: (libc)BSD Random.
* rawmemchr: (libc)Search Functions.
* read: (libc)I/O Primitives.
* readdir64: (libc)Reading/Closing Directory.
* readdir64_r: (libc)Reading/Closing Directory.
* readdir: (libc)Reading/Closing Directory.
* readdir_r: (libc)Reading/Closing Directory.
* readlink: (libc)Symbolic Links.
* readv: (libc)Scatter-Gather.
* realloc: (libc)Changing Block Size.
* realpath: (libc)Symbolic Links.
* recv: (libc)Receiving Data.
* recvfrom: (libc)Receiving Datagrams.
* recvmsg: (libc)Receiving Datagrams.
* regcomp: (libc)POSIX Regexp Compilation.
* regerror: (libc)Regexp Cleanup.
* regexec: (libc)Matching POSIX Regexps.
* regfree: (libc)Regexp Cleanup.
* register_printf_function: (libc)Registering New Conversions.
* remainder: (libc)Remainder Functions.
* remainderf: (libc)Remainder Functions.
* remainderl: (libc)Remainder Functions.
* remove: (libc)Deleting Files.
* rename: (libc)Renaming Files.
* rewind: (libc)File Positioning.
* rewinddir: (libc)Random Access Directory.
* rindex: (libc)Search Functions.
* rint: (libc)Rounding Functions.
* rintf: (libc)Rounding Functions.
* rintl: (libc)Rounding Functions.
* rmdir: (libc)Deleting Files.
* round: (libc)Rounding Functions.
* roundf: (libc)Rounding Functions.
* roundl: (libc)Rounding Functions.
* rpmatch: (libc)Yes-or-No Questions.
* sbrk: (libc)Resizing the Data Segment.
* scalb: (libc)Normalization Functions.
* scalbf: (libc)Normalization Functions.
* scalbl: (libc)Normalization Functions.
* scalbln: (libc)Normalization Functions.
* scalblnf: (libc)Normalization Functions.
* scalblnl: (libc)Normalization Functions.
* scalbn: (libc)Normalization Functions.
* scalbnf: (libc)Normalization Functions.
* scalbnl: (libc)Normalization Functions.
* scandir64: (libc)Scanning Directory Content.
* scandir: (libc)Scanning Directory Content.
* scanf: (libc)Formatted Input Functions.
* sched_get_priority_max: (libc)Basic Scheduling Functions.
* sched_get_priority_min: (libc)Basic Scheduling Functions.
* sched_getaffinity: (libc)CPU Affinity.
* sched_getparam: (libc)Basic Scheduling Functions.
* sched_getscheduler: (libc)Basic Scheduling Functions.
* sched_rr_get_interval: (libc)Basic Scheduling Functions.
* sched_setaffinity: (libc)CPU Affinity.
* sched_setparam: (libc)Basic Scheduling Functions.
* sched_setscheduler: (libc)Basic Scheduling Functions.
* sched_yield: (libc)Basic Scheduling Functions.
* secure_getenv: (libc)Environment Access.
* seed48: (libc)SVID Random.
* seed48_r: (libc)SVID Random.
* seekdir: (libc)Random Access Directory.
* select: (libc)Waiting for I/O.
* send: (libc)Sending Data.
* sendmsg: (libc)Receiving Datagrams.
* sendto: (libc)Sending Datagrams.
* setbuf: (libc)Controlling Buffering.
* setbuffer: (libc)Controlling Buffering.
* setcontext: (libc)System V contexts.
* setdomainname: (libc)Host Identification.
* setegid: (libc)Setting Groups.
* setenv: (libc)Environment Access.
* seteuid: (libc)Setting User ID.
* setfsent: (libc)fstab.
* setgid: (libc)Setting Groups.
* setgrent: (libc)Scanning All Groups.
* setgroups: (libc)Setting Groups.
* sethostent: (libc)Host Names.
* sethostid: (libc)Host Identification.
* sethostname: (libc)Host Identification.
* setitimer: (libc)Setting an Alarm.
* setjmp: (libc)Non-Local Details.
* setkey: (libc)DES Encryption.
* setkey_r: (libc)DES Encryption.
* setlinebuf: (libc)Controlling Buffering.
* setlocale: (libc)Setting the Locale.
* setlogmask: (libc)setlogmask.
* setmntent: (libc)mtab.
* setnetent: (libc)Networks Database.
* setnetgrent: (libc)Lookup Netgroup.
* setpgid: (libc)Process Group Functions.
* setpgrp: (libc)Process Group Functions.
* setpriority: (libc)Traditional Scheduling Functions.
* setprotoent: (libc)Protocols Database.
* setpwent: (libc)Scanning All Users.
* setregid: (libc)Setting Groups.
* setreuid: (libc)Setting User ID.
* setrlimit64: (libc)Limits on Resources.
* setrlimit: (libc)Limits on Resources.
* setservent: (libc)Services Database.
* setsid: (libc)Process Group Functions.
* setsockopt: (libc)Socket Option Functions.
* setstate: (libc)BSD Random.
* setstate_r: (libc)BSD Random.
* settimeofday: (libc)High-Resolution Calendar.
* setuid: (libc)Setting User ID.
* setutent: (libc)Manipulating the Database.
* setutxent: (libc)XPG Functions.
* setvbuf: (libc)Controlling Buffering.
* shm_open: (libc)Memory-mapped I/O.
* shm_unlink: (libc)Memory-mapped I/O.
* shutdown: (libc)Closing a Socket.
* sigaction: (libc)Advanced Signal Handling.
* sigaddset: (libc)Signal Sets.
* sigaltstack: (libc)Signal Stack.
* sigblock: (libc)Blocking in BSD.
* sigdelset: (libc)Signal Sets.
* sigemptyset: (libc)Signal Sets.
* sigfillset: (libc)Signal Sets.
* siginterrupt: (libc)BSD Handler.
* sigismember: (libc)Signal Sets.
* siglongjmp: (libc)Non-Local Exits and Signals.
* sigmask: (libc)Blocking in BSD.
* signal: (libc)Basic Signal Handling.
* signbit: (libc)FP Bit Twiddling.
* significand: (libc)Normalization Functions.
* significandf: (libc)Normalization Functions.
* significandl: (libc)Normalization Functions.
* sigpause: (libc)Blocking in BSD.
* sigpending: (libc)Checking for Pending Signals.
* sigprocmask: (libc)Process Signal Mask.
* sigsetjmp: (libc)Non-Local Exits and Signals.
* sigsetmask: (libc)Blocking in BSD.
* sigstack: (libc)Signal Stack.
* sigsuspend: (libc)Sigsuspend.
* sigvec: (libc)BSD Handler.
* sin: (libc)Trig Functions.
* sincos: (libc)Trig Functions.
* sincosf: (libc)Trig Functions.
* sincosl: (libc)Trig Functions.
* sinf: (libc)Trig Functions.
* sinh: (libc)Hyperbolic Functions.
* sinhf: (libc)Hyperbolic Functions.
* sinhl: (libc)Hyperbolic Functions.
* sinl: (libc)Trig Functions.
* sleep: (libc)Sleeping.
* snprintf: (libc)Formatted Output Functions.
* socket: (libc)Creating a Socket.
* socketpair: (libc)Socket Pairs.
* sprintf: (libc)Formatted Output Functions.
* sqrt: (libc)Exponents and Logarithms.
* sqrtf: (libc)Exponents and Logarithms.
* sqrtl: (libc)Exponents and Logarithms.
* srand48: (libc)SVID Random.
* srand48_r: (libc)SVID Random.
* srand: (libc)ISO Random.
* srandom: (libc)BSD Random.
* srandom_r: (libc)BSD Random.
* sscanf: (libc)Formatted Input Functions.
* ssignal: (libc)Basic Signal Handling.
* stat64: (libc)Reading Attributes.
* stat: (libc)Reading Attributes.
* stime: (libc)Simple Calendar Time.
* stpcpy: (libc)Copying and Concatenation.
* stpncpy: (libc)Copying and Concatenation.
* strcasecmp: (libc)String/Array Comparison.
* strcasestr: (libc)Search Functions.
* strcat: (libc)Copying and Concatenation.
* strchr: (libc)Search Functions.
* strchrnul: (libc)Search Functions.
* strcmp: (libc)String/Array Comparison.
* strcoll: (libc)Collation Functions.
* strcpy: (libc)Copying and Concatenation.
* strcspn: (libc)Search Functions.
* strdup: (libc)Copying and Concatenation.
* strdupa: (libc)Copying and Concatenation.
* strerror: (libc)Error Messages.
* strerror_r: (libc)Error Messages.
* strfmon: (libc)Formatting Numbers.
* strfry: (libc)strfry.
* strftime: (libc)Formatting Calendar Time.
* strlen: (libc)String Length.
* strncasecmp: (libc)String/Array Comparison.
* strncat: (libc)Copying and Concatenation.
* strncmp: (libc)String/Array Comparison.
* strncpy: (libc)Copying and Concatenation.
* strndup: (libc)Copying and Concatenation.
* strndupa: (libc)Copying and Concatenation.
* strnlen: (libc)String Length.
* strpbrk: (libc)Search Functions.
* strptime: (libc)Low-Level Time String Parsing.
* strrchr: (libc)Search Functions.
* strsep: (libc)Finding Tokens in a String.
* strsignal: (libc)Signal Messages.
* strspn: (libc)Search Functions.
* strstr: (libc)Search Functions.
* strtod: (libc)Parsing of Floats.
* strtof: (libc)Parsing of Floats.
* strtoimax: (libc)Parsing of Integers.
* strtok: (libc)Finding Tokens in a String.
* strtok_r: (libc)Finding Tokens in a String.
* strtol: (libc)Parsing of Integers.
* strtold: (libc)Parsing of Floats.
* strtoll: (libc)Parsing of Integers.
* strtoq: (libc)Parsing of Integers.
* strtoul: (libc)Parsing of Integers.
* strtoull: (libc)Parsing of Integers.
* strtoumax: (libc)Parsing of Integers.
* strtouq: (libc)Parsing of Integers.
* strverscmp: (libc)String/Array Comparison.
* strxfrm: (libc)Collation Functions.
* stty: (libc)BSD Terminal Modes.
* swapcontext: (libc)System V contexts.
* swprintf: (libc)Formatted Output Functions.
* swscanf: (libc)Formatted Input Functions.
* symlink: (libc)Symbolic Links.
* sync: (libc)Synchronizing I/O.
* syscall: (libc)System Calls.
* sysconf: (libc)Sysconf Definition.
* sysctl: (libc)System Parameters.
* syslog: (libc)syslog; vsyslog.
* system: (libc)Running a Command.
* sysv_signal: (libc)Basic Signal Handling.
* tan: (libc)Trig Functions.
* tanf: (libc)Trig Functions.
* tanh: (libc)Hyperbolic Functions.
* tanhf: (libc)Hyperbolic Functions.
* tanhl: (libc)Hyperbolic Functions.
* tanl: (libc)Trig Functions.
* tcdrain: (libc)Line Control.
* tcflow: (libc)Line Control.
* tcflush: (libc)Line Control.
* tcgetattr: (libc)Mode Functions.
* tcgetpgrp: (libc)Terminal Access Functions.
* tcgetsid: (libc)Terminal Access Functions.
* tcsendbreak: (libc)Line Control.
* tcsetattr: (libc)Mode Functions.
* tcsetpgrp: (libc)Terminal Access Functions.
* tdelete: (libc)Tree Search Function.
* tdestroy: (libc)Tree Search Function.
* telldir: (libc)Random Access Directory.
* tempnam: (libc)Temporary Files.
* textdomain: (libc)Locating gettext catalog.
* tfind: (libc)Tree Search Function.
* tgamma: (libc)Special Functions.
* tgammaf: (libc)Special Functions.
* tgammal: (libc)Special Functions.
* time: (libc)Simple Calendar Time.
* timegm: (libc)Broken-down Time.
* timelocal: (libc)Broken-down Time.
* times: (libc)Processor Time.
* tmpfile64: (libc)Temporary Files.
* tmpfile: (libc)Temporary Files.
* tmpnam: (libc)Temporary Files.
* tmpnam_r: (libc)Temporary Files.
* toascii: (libc)Case Conversion.
* tolower: (libc)Case Conversion.
* toupper: (libc)Case Conversion.
* towctrans: (libc)Wide Character Case Conversion.
* towlower: (libc)Wide Character Case Conversion.
* towupper: (libc)Wide Character Case Conversion.
* trunc: (libc)Rounding Functions.
* truncate64: (libc)File Size.
* truncate: (libc)File Size.
* truncf: (libc)Rounding Functions.
* truncl: (libc)Rounding Functions.
* tsearch: (libc)Tree Search Function.
* ttyname: (libc)Is It a Terminal.
* ttyname_r: (libc)Is It a Terminal.
* twalk: (libc)Tree Search Function.
* tzset: (libc)Time Zone Functions.
* ulimit: (libc)Limits on Resources.
* umask: (libc)Setting Permissions.
* umount2: (libc)Mount-Unmount-Remount.
* umount: (libc)Mount-Unmount-Remount.
* uname: (libc)Platform Type.
* ungetc: (libc)How Unread.
* ungetwc: (libc)How Unread.
* unlink: (libc)Deleting Files.
* unlockpt: (libc)Allocation.
* unsetenv: (libc)Environment Access.
* updwtmp: (libc)Manipulating the Database.
* utime: (libc)File Times.
* utimes: (libc)File Times.
* utmpname: (libc)Manipulating the Database.
* utmpxname: (libc)XPG Functions.
* va_arg: (libc)Argument Macros.
* va_copy: (libc)Argument Macros.
* va_end: (libc)Argument Macros.
* va_start: (libc)Argument Macros.
* valloc: (libc)Aligned Memory Blocks.
* vasprintf: (libc)Variable Arguments Output.
* verr: (libc)Error Messages.
* verrx: (libc)Error Messages.
* versionsort64: (libc)Scanning Directory Content.
* versionsort: (libc)Scanning Directory Content.
* vfork: (libc)Creating a Process.
* vfprintf: (libc)Variable Arguments Output.
* vfscanf: (libc)Variable Arguments Input.
* vfwprintf: (libc)Variable Arguments Output.
* vfwscanf: (libc)Variable Arguments Input.
* vlimit: (libc)Limits on Resources.
* vprintf: (libc)Variable Arguments Output.
* vscanf: (libc)Variable Arguments Input.
* vsnprintf: (libc)Variable Arguments Output.
* vsprintf: (libc)Variable Arguments Output.
* vsscanf: (libc)Variable Arguments Input.
* vswprintf: (libc)Variable Arguments Output.
* vswscanf: (libc)Variable Arguments Input.
* vsyslog: (libc)syslog; vsyslog.
* vtimes: (libc)Resource Usage.
* vwarn: (libc)Error Messages.
* vwarnx: (libc)Error Messages.
* vwprintf: (libc)Variable Arguments Output.
* vwscanf: (libc)Variable Arguments Input.
* wait3: (libc)BSD Wait Functions.
* wait4: (libc)Process Completion.
* wait: (libc)Process Completion.
* waitpid: (libc)Process Completion.
* warn: (libc)Error Messages.
* warnx: (libc)Error Messages.
* wcpcpy: (libc)Copying and Concatenation.
* wcpncpy: (libc)Copying and Concatenation.
* wcrtomb: (libc)Converting a Character.
* wcscasecmp: (libc)String/Array Comparison.
* wcscat: (libc)Copying and Concatenation.
* wcschr: (libc)Search Functions.
* wcschrnul: (libc)Search Functions.
* wcscmp: (libc)String/Array Comparison.
* wcscoll: (libc)Collation Functions.
* wcscpy: (libc)Copying and Concatenation.
* wcscspn: (libc)Search Functions.
* wcsdup: (libc)Copying and Concatenation.
* wcsftime: (libc)Formatting Calendar Time.
* wcslen: (libc)String Length.
* wcsncasecmp: (libc)String/Array Comparison.
* wcsncat: (libc)Copying and Concatenation.
* wcsncmp: (libc)String/Array Comparison.
* wcsncpy: (libc)Copying and Concatenation.
* wcsnlen: (libc)String Length.
* wcsnrtombs: (libc)Converting Strings.
* wcspbrk: (libc)Search Functions.
* wcsrchr: (libc)Search Functions.
* wcsrtombs: (libc)Converting Strings.
* wcsspn: (libc)Search Functions.
* wcsstr: (libc)Search Functions.
* wcstod: (libc)Parsing of Floats.
* wcstof: (libc)Parsing of Floats.
* wcstoimax: (libc)Parsing of Integers.
* wcstok: (libc)Finding Tokens in a String.
* wcstol: (libc)Parsing of Integers.
* wcstold: (libc)Parsing of Floats.
* wcstoll: (libc)Parsing of Integers.
* wcstombs: (libc)Non-reentrant String Conversion.
* wcstoq: (libc)Parsing of Integers.
* wcstoul: (libc)Parsing of Integers.
* wcstoull: (libc)Parsing of Integers.
* wcstoumax: (libc)Parsing of Integers.
* wcstouq: (libc)Parsing of Integers.
* wcswcs: (libc)Search Functions.
* wcsxfrm: (libc)Collation Functions.
* wctob: (libc)Converting a Character.
* wctomb: (libc)Non-reentrant Character Conversion.
* wctrans: (libc)Wide Character Case Conversion.
* wctype: (libc)Classification of Wide Characters.
* wmemchr: (libc)Search Functions.
* wmemcmp: (libc)String/Array Comparison.
* wmemcpy: (libc)Copying and Concatenation.
* wmemmove: (libc)Copying and Concatenation.
* wmempcpy: (libc)Copying and Concatenation.
* wmemset: (libc)Copying and Concatenation.
* wordexp: (libc)Calling Wordexp.
* wordfree: (libc)Calling Wordexp.
* wprintf: (libc)Formatted Output Functions.
* write: (libc)I/O Primitives.
* writev: (libc)Scatter-Gather.
* wscanf: (libc)Formatted Input Functions.
* y0: (libc)Special Functions.
* y0f: (libc)Special Functions.
* y0l: (libc)Special Functions.
* y1: (libc)Special Functions.
* y1f: (libc)Special Functions.
* y1l: (libc)Special Functions.
* yn: (libc)Special Functions.
* ynf: (libc)Special Functions.
* ynl: (libc)Special Functions.
END-INFO-DIR-ENTRY

File: libc.info, Node: Argp Examples, Next: Argp User Customization, Prev: Argp Help, Up: Argp
25.3.11 Argp Examples
---------------------
These example programs demonstrate the basic usage of argp.
* Menu:
* 1: Argp Example 1. A minimal program using argp.
* 2: Argp Example 2. A program using only default options.
* 3: Argp Example 3. A simple program with user options.
* 4: Argp Example 4. Combining multiple argp parsers.

File: libc.info, Node: Argp Example 1, Next: Argp Example 2, Up: Argp Examples
25.3.11.1 A Minimal Program Using Argp
......................................
This is perhaps the smallest program possible that uses argp. It won't
do much except give an error messages and exit when there are any
arguments, and prints a rather pointless message for '--help'.
/* This is (probably) the smallest possible program that
uses argp. It won't do much except give an error
messages and exit when there are any arguments, and print
a (rather pointless) messages for -help. */
#include <stdlib.h>
#include <argp.h>
int
main (int argc, char **argv)
{
argp_parse (0, argc, argv, 0, 0, 0);
exit (0);
}

File: libc.info, Node: Argp Example 2, Next: Argp Example 3, Prev: Argp Example 1, Up: Argp Examples
25.3.11.2 A Program Using Argp with Only Default Options
........................................................
This program doesn't use any options or arguments, it uses argp to be
compliant with the GNU standard command line format.
In addition to giving no arguments and implementing a '--help'
option, this example has a '--version' option, which will put the given
documentation string and bug address in the '--help' output, as per GNU
standards.
The variable 'argp' contains the argument parser specification.
Adding fields to this structure is the way most parameters are passed to
'argp_parse'. The first three fields are normally used, but they are
not in this small program. There are also two global variables that
argp can use defined here, 'argp_program_version' and
'argp_program_bug_address'. They are considered global variables
because they will almost always be constant for a given program, even if
they use different argument parsers for various tasks.
/* This program doesn't use any options or arguments, but uses
argp to be compliant with the GNU standard command line
format.
In addition to making sure no arguments are given, and
implementing a -help option, this example will have a
-version option, and will put the given documentation string
and bug address in the -help output, as per GNU standards.
The variable ARGP contains the argument parser specification;
adding fields to this structure is the way most parameters are
passed to argp_parse (the first three fields are usually used,
but not in this small program). There are also two global
variables that argp knows about defined here,
ARGP_PROGRAM_VERSION and ARGP_PROGRAM_BUG_ADDRESS (they are
global variables because they will almost always be constant
for a given program, even if it uses different argument
parsers for various tasks). */
#include <stdlib.h>
#include <argp.h>
const char *argp_program_version =
"argp-ex2 1.0";
const char *argp_program_bug_address =
"<bug-gnu-utils@gnu.org>";
/* Program documentation. */
static char doc[] =
"Argp example #2 -- a pretty minimal program using argp";
/* Our argument parser. The 'options', 'parser', and
'args_doc' fields are zero because we have neither options or
arguments; 'doc' and 'argp_program_bug_address' will be
used in the output for '--help', and the '--version'
option will print out 'argp_program_version'. */
static struct argp argp = { 0, 0, 0, doc };
int
main (int argc, char **argv)
{
argp_parse (&argp, argc, argv, 0, 0, 0);
exit (0);
}

File: libc.info, Node: Argp Example 3, Next: Argp Example 4, Prev: Argp Example 2, Up: Argp Examples
25.3.11.3 A Program Using Argp with User Options
................................................
This program uses the same features as example 2, adding user options
and arguments.
We now use the first four fields in 'argp' (*note Argp Parsers::) and
specify 'parse_opt' as the parser function. *Note Argp Parser
Functions::.
Note that in this example, 'main' uses a structure to communicate
with the 'parse_opt' function, a pointer to which it passes in the
'input' argument to 'argp_parse'. *Note Argp::. It is retrieved by
'parse_opt' through the 'input' field in its 'state' argument. *Note
Argp Parsing State::. Of course, it's also possible to use global
variables instead, but using a structure like this is somewhat more
flexible and clean.
/* This program uses the same features as example 2, and uses options and
arguments.
We now use the first four fields in ARGP, so here's a description of them:
OPTIONS - A pointer to a vector of struct argp_option (see below)
PARSER - A function to parse a single option, called by argp
ARGS_DOC - A string describing how the non-option arguments should look
DOC - A descriptive string about this program; if it contains a
vertical tab character (\v), the part after it will be
printed *following* the options
The function PARSER takes the following arguments:
KEY - An integer specifying which option this is (taken
from the KEY field in each struct argp_option), or
a special key specifying something else; the only
special keys we use here are ARGP_KEY_ARG, meaning
a non-option argument, and ARGP_KEY_END, meaning
that all arguments have been parsed
ARG - For an option KEY, the string value of its
argument, or NULL if it has none
STATE- A pointer to a struct argp_state, containing
various useful information about the parsing state; used here
are the INPUT field, which reflects the INPUT argument to
argp_parse, and the ARG_NUM field, which is the number of the
current non-option argument being parsed
It should return either 0, meaning success, ARGP_ERR_UNKNOWN, meaning the
given KEY wasn't recognized, or an errno value indicating some other
error.
Note that in this example, main uses a structure to communicate with the
parse_opt function, a pointer to which it passes in the INPUT argument to
argp_parse. Of course, it's also possible to use global variables
instead, but this is somewhat more flexible.
The OPTIONS field contains a pointer to a vector of struct argp_option's;
that structure has the following fields (if you assign your option
structures using array initialization like this example, unspecified
fields will be defaulted to 0, and need not be specified):
NAME - The name of this option's long option (may be zero)
KEY - The KEY to pass to the PARSER function when parsing this option,
*and* the name of this option's short option, if it is a
printable ascii character
ARG - The name of this option's argument, if any
FLAGS - Flags describing this option; some of them are:
OPTION_ARG_OPTIONAL - The argument to this option is optional
OPTION_ALIAS - This option is an alias for the
previous option
OPTION_HIDDEN - Don't show this option in -help output
DOC - A documentation string for this option, shown in -help output
An options vector should be terminated by an option with all fields zero. */
#include <stdlib.h>
#include <argp.h>
const char *argp_program_version =
"argp-ex3 1.0";
const char *argp_program_bug_address =
"<bug-gnu-utils@gnu.org>";
/* Program documentation. */
static char doc[] =
"Argp example #3 -- a program with options and arguments using argp";
/* A description of the arguments we accept. */
static char args_doc[] = "ARG1 ARG2";
/* The options we understand. */
static struct argp_option options[] = {
{"verbose", 'v', 0, 0, "Produce verbose output" },
{"quiet", 'q', 0, 0, "Don't produce any output" },
{"silent", 's', 0, OPTION_ALIAS },
{"output", 'o', "FILE", 0,
"Output to FILE instead of standard output" },
{ 0 }
};
/* Used by 'main' to communicate with 'parse_opt'. */
struct arguments
{
char *args[2]; /* ARG1 & ARG2 */
int silent, verbose;
char *output_file;
};
/* Parse a single option. */
static error_t
parse_opt (int key, char *arg, struct argp_state *state)
{
/* Get the INPUT argument from 'argp_parse', which we
know is a pointer to our arguments structure. */
struct arguments *arguments = state->input;
switch (key)
{
case 'q': case 's':
arguments->silent = 1;
break;
case 'v':
arguments->verbose = 1;
break;
case 'o':
arguments->output_file = arg;
break;
case ARGP_KEY_ARG:
if (state->arg_num >= 2)
/* Too many arguments. */
argp_usage (state);
arguments->args[state->arg_num] = arg;
break;
case ARGP_KEY_END:
if (state->arg_num < 2)
/* Not enough arguments. */
argp_usage (state);
break;
default:
return ARGP_ERR_UNKNOWN;
}
return 0;
}
/* Our argp parser. */
static struct argp argp = { options, parse_opt, args_doc, doc };
int
main (int argc, char **argv)
{
struct arguments arguments;
/* Default values. */
arguments.silent = 0;
arguments.verbose = 0;
arguments.output_file = "-";
/* Parse our arguments; every option seen by 'parse_opt' will
be reflected in 'arguments'. */
argp_parse (&argp, argc, argv, 0, 0, &arguments);
printf ("ARG1 = %s\nARG2 = %s\nOUTPUT_FILE = %s\n"
"VERBOSE = %s\nSILENT = %s\n",
arguments.args[0], arguments.args[1],
arguments.output_file,
arguments.verbose ? "yes" : "no",
arguments.silent ? "yes" : "no");
exit (0);
}

File: libc.info, Node: Argp Example 4, Prev: Argp Example 3, Up: Argp Examples
25.3.11.4 A Program Using Multiple Combined Argp Parsers
........................................................
This program uses the same features as example 3, but has more options,
and presents more structure in the '--help' output. It also illustrates
how you can 'steal' the remainder of the input arguments past a certain
point for programs that accept a list of items. It also illustrates the
KEY value 'ARGP_KEY_NO_ARGS', which is only given if no non-option
arguments were supplied to the program. *Note Argp Special Keys::.
For structuring help output, two features are used: _headers_ and a
two part option string. The _headers_ are entries in the options
vector. *Note Argp Option Vectors::. The first four fields are zero.
The two part documentation string are in the variable 'doc', which
allows documentation both before and after the options. *Note Argp
Parsers::, the two parts of 'doc' are separated by a vertical-tab
character (''\v'', or ''\013''). By convention, the documentation
before the options is a short string stating what the program does, and
after any options it is longer, describing the behavior in more detail.
All documentation strings are automatically filled for output, although
newlines may be included to force a line break at a particular point.
In addition, documentation strings are passed to the 'gettext' function,
for possible translation into the current locale.
/* This program uses the same features as example 3, but has more
options, and somewhat more structure in the -help output. It
also shows how you can 'steal' the remainder of the input
arguments past a certain point, for programs that accept a
list of items. It also shows the special argp KEY value
ARGP_KEY_NO_ARGS, which is only given if no non-option
arguments were supplied to the program.
For structuring the help output, two features are used,
*headers* which are entries in the options vector with the
first four fields being zero, and a two part documentation
string (in the variable DOC), which allows documentation both
before and after the options; the two parts of DOC are
separated by a vertical-tab character ('\v', or '\013'). By
convention, the documentation before the options is just a
short string saying what the program does, and that afterwards
is longer, describing the behavior in more detail. All
documentation strings are automatically filled for output,
although newlines may be included to force a line break at a
particular point. All documentation strings are also passed to
the 'gettext' function, for possible translation into the
current locale. */
#include <stdlib.h>
#include <error.h>
#include <argp.h>
const char *argp_program_version =
"argp-ex4 1.0";
const char *argp_program_bug_address =
"<bug-gnu-utils@prep.ai.mit.edu>";
/* Program documentation. */
static char doc[] =
"Argp example #4 -- a program with somewhat more complicated\
options\
\vThis part of the documentation comes *after* the options;\
note that the text is automatically filled, but it's possible\
to force a line-break, e.g.\n<-- here.";
/* A description of the arguments we accept. */
static char args_doc[] = "ARG1 [STRING...]";
/* Keys for options without short-options. */
#define OPT_ABORT 1 /* -abort */
/* The options we understand. */
static struct argp_option options[] = {
{"verbose", 'v', 0, 0, "Produce verbose output" },
{"quiet", 'q', 0, 0, "Don't produce any output" },
{"silent", 's', 0, OPTION_ALIAS },
{"output", 'o', "FILE", 0,
"Output to FILE instead of standard output" },
{0,0,0,0, "The following options should be grouped together:" },
{"repeat", 'r', "COUNT", OPTION_ARG_OPTIONAL,
"Repeat the output COUNT (default 10) times"},
{"abort", OPT_ABORT, 0, 0, "Abort before showing any output"},
{ 0 }
};
/* Used by 'main' to communicate with 'parse_opt'. */
struct arguments
{
char *arg1; /* ARG1 */
char **strings; /* [STRING...] */
int silent, verbose, abort; /* '-s', '-v', '--abort' */
char *output_file; /* FILE arg to '--output' */
int repeat_count; /* COUNT arg to '--repeat' */
};
/* Parse a single option. */
static error_t
parse_opt (int key, char *arg, struct argp_state *state)
{
/* Get the 'input' argument from 'argp_parse', which we
know is a pointer to our arguments structure. */
struct arguments *arguments = state->input;
switch (key)
{
case 'q': case 's':
arguments->silent = 1;
break;
case 'v':
arguments->verbose = 1;
break;
case 'o':
arguments->output_file = arg;
break;
case 'r':
arguments->repeat_count = arg ? atoi (arg) : 10;
break;
case OPT_ABORT:
arguments->abort = 1;
break;
case ARGP_KEY_NO_ARGS:
argp_usage (state);
case ARGP_KEY_ARG:
/* Here we know that 'state->arg_num == 0', since we
force argument parsing to end before any more arguments can
get here. */
arguments->arg1 = arg;
/* Now we consume all the rest of the arguments.
'state->next' is the index in 'state->argv' of the
next argument to be parsed, which is the first STRING
we're interested in, so we can just use
'&state->argv[state->next]' as the value for
arguments->strings.
_In addition_, by setting 'state->next' to the end
of the arguments, we can force argp to stop parsing here and
return. */
arguments->strings = &state->argv[state->next];
state->next = state->argc;
break;
default:
return ARGP_ERR_UNKNOWN;
}
return 0;
}
/* Our argp parser. */
static struct argp argp = { options, parse_opt, args_doc, doc };
int
main (int argc, char **argv)
{
int i, j;
struct arguments arguments;
/* Default values. */
arguments.silent = 0;
arguments.verbose = 0;
arguments.output_file = "-";
arguments.repeat_count = 1;
arguments.abort = 0;
/* Parse our arguments; every option seen by 'parse_opt' will be
reflected in 'arguments'. */
argp_parse (&argp, argc, argv, 0, 0, &arguments);
if (arguments.abort)
error (10, 0, "ABORTED");
for (i = 0; i < arguments.repeat_count; i++)
{
printf ("ARG1 = %s\n", arguments.arg1);
printf ("STRINGS = ");
for (j = 0; arguments.strings[j]; j++)
printf (j == 0 ? "%s" : ", %s", arguments.strings[j]);
printf ("\n");
printf ("OUTPUT_FILE = %s\nVERBOSE = %s\nSILENT = %s\n",
arguments.output_file,
arguments.verbose ? "yes" : "no",
arguments.silent ? "yes" : "no");
}
exit (0);
}

File: libc.info, Node: Argp User Customization, Prev: Argp Examples, Up: Argp
25.3.12 Argp User Customization
-------------------------------
The formatting of argp '--help' output may be controlled to some extent
by a program's users, by setting the 'ARGP_HELP_FMT' environment
variable to a comma-separated list of tokens. Whitespace is ignored:
'dup-args'
'no-dup-args'
These turn "duplicate-argument-mode" on or off. In duplicate
argument mode, if an option that accepts an argument has multiple
names, the argument is shown for each name. Otherwise, it is only
shown for the first long option. A note is subsequently printed so
the user knows that it applies to other names as well. The default
is 'no-dup-args', which is less consistent, but prettier.
'dup-args-note'
'no-dup-args-note'
These will enable or disable the note informing the user of
suppressed option argument duplication. The default is
'dup-args-note'.
'short-opt-col=N'
This prints the first short option in column N. The default is 2.
'long-opt-col=N'
This prints the first long option in column N. The default is 6.
'doc-opt-col=N'
This prints 'documentation options' (*note Argp Option Flags::) in
column N. The default is 2.
'opt-doc-col=N'
This prints the documentation for options starting in column N.
The default is 29.
'header-col=N'
This will indent the group headers that document groups of options
to column N. The default is 1.
'usage-indent=N'
This will indent continuation lines in 'Usage:' messages to column
N. The default is 12.
'rmargin=N'
This will word wrap help output at or before column N. The default
is 79.

File: libc.info, Node: Suboptions, Next: Suboptions Example, Prev: Argp, Up: Parsing Program Arguments
25.3.12.1 Parsing of Suboptions
...............................
Having a single level of options is sometimes not enough. There might
be too many options which have to be available or a set of options is
closely related.
For this case some programs use suboptions. One of the most
prominent programs is certainly 'mount'(8). The '-o' option take one
argument which itself is a comma separated list of options. To ease the
programming of code like this the function 'getsubopt' is available.
-- Function: int getsubopt (char **OPTIONP, char *const *TOKENS, char
**VALUEP)
Preliminary: | MT-Safe | AS-Safe | AC-Safe | *Note POSIX Safety
Concepts::.
The OPTIONP parameter must be a pointer to a variable containing
the address of the string to process. When the function returns
the reference is updated to point to the next suboption or to the
terminating '\0' character if there is no more suboption available.
The TOKENS parameter references an array of strings containing the
known suboptions. All strings must be '\0' terminated and to mark
the end a null pointer must be stored. When 'getsubopt' finds a
possible legal suboption it compares it with all strings available
in the TOKENS array and returns the index in the string as the
indicator.
In case the suboption has an associated value introduced by a '='
character, a pointer to the value is returned in VALUEP. The
string is '\0' terminated. If no argument is available VALUEP is
set to the null pointer. By doing this the caller can check
whether a necessary value is given or whether no unexpected value
is present.
In case the next suboption in the string is not mentioned in the
TOKENS array the starting address of the suboption including a
possible value is returned in VALUEP and the return value of the
function is '-1'.

File: libc.info, Node: Suboptions Example, Prev: Suboptions, Up: Parsing Program Arguments
25.3.13 Parsing of Suboptions Example
-------------------------------------
The code which might appear in the 'mount'(8) program is a perfect
example of the use of 'getsubopt':
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
int do_all;
const char *type;
int read_size;
int write_size;
int read_only;
enum
{
RO_OPTION = 0,
RW_OPTION,
READ_SIZE_OPTION,
WRITE_SIZE_OPTION,
THE_END
};
const char *mount_opts[] =
{
[RO_OPTION] = "ro",
[RW_OPTION] = "rw",
[READ_SIZE_OPTION] = "rsize",
[WRITE_SIZE_OPTION] = "wsize",
[THE_END] = NULL
};
int
main (int argc, char **argv)
{
char *subopts, *value;
int opt;
while ((opt = getopt (argc, argv, "at:o:")) != -1)
switch (opt)
{
case 'a':
do_all = 1;
break;
case 't':
type = optarg;
break;
case 'o':
subopts = optarg;
while (*subopts != '\0')
switch (getsubopt (&subopts, mount_opts, &value))
{
case RO_OPTION:
read_only = 1;
break;
case RW_OPTION:
read_only = 0;
break;
case READ_SIZE_OPTION:
if (value == NULL)
abort ();
read_size = atoi (value);
break;
case WRITE_SIZE_OPTION:
if (value == NULL)
abort ();
write_size = atoi (value);
break;
default:
/* Unknown suboption. */
printf ("Unknown suboption `%s'\n", value);
break;
}
break;
default:
abort ();
}
/* Do the real work. */
return 0;
}

File: libc.info, Node: Environment Variables, Next: Auxiliary Vector, Prev: Program Arguments, Up: Program Basics
25.4 Environment Variables
==========================
When a program is executed, it receives information about the context in
which it was invoked in two ways. The first mechanism uses the ARGV and
ARGC arguments to its 'main' function, and is discussed in *note Program
Arguments::. The second mechanism uses "environment variables" and is
discussed in this section.
The ARGV mechanism is typically used to pass command-line arguments
specific to the particular program being invoked. The environment, on
the other hand, keeps track of information that is shared by many
programs, changes infrequently, and that is less frequently used.
The environment variables discussed in this section are the same
environment variables that you set using assignments and the 'export'
command in the shell. Programs executed from the shell inherit all of
the environment variables from the shell.
Standard environment variables are used for information about the
user's home directory, terminal type, current locale, and so on; you can
define additional variables for other purposes. The set of all
environment variables that have values is collectively known as the
"environment".
Names of environment variables are case-sensitive and must not
contain the character '='. System-defined environment variables are
invariably uppercase.
The values of environment variables can be anything that can be
represented as a string. A value must not contain an embedded null
character, since this is assumed to terminate the string.
* Menu:
* Environment Access:: How to get and set the values of
environment variables.
* Standard Environment:: These environment variables have
standard interpretations.

File: libc.info, Node: Environment Access, Next: Standard Environment, Up: Environment Variables
25.4.1 Environment Access
-------------------------
The value of an environment variable can be accessed with the 'getenv'
function. This is declared in the header file 'stdlib.h'.
Libraries should use 'secure_getenv' instead of 'getenv', so that
they do not accidentally use untrusted environment variables.
Modifications of environment variables are not allowed in multi-threaded
programs. The 'getenv' and 'secure_getenv' functions can be safely used
in multi-threaded programs.
-- Function: char * getenv (const char *NAME)
Preliminary: | MT-Safe env | AS-Safe | AC-Safe | *Note POSIX Safety
Concepts::.
This function returns a string that is the value of the environment
variable NAME. You must not modify this string. In some non-Unix
systems not using the GNU C Library, it might be overwritten by
subsequent calls to 'getenv' (but not by any other library
function). If the environment variable NAME is not defined, the
value is a null pointer.
-- Function: char * secure_getenv (const char *NAME)
Preliminary: | MT-Safe env | AS-Safe | AC-Safe | *Note POSIX Safety
Concepts::.
This function is similar to 'getenv', but it returns a null pointer
if the environment is untrusted. This happens when the program
file has SUID or SGID bits set. General-purpose libraries should
always prefer this function over 'getenv' to avoid vulnerabilities
if the library is referenced from a SUID/SGID program.
This function is a GNU extension.
-- Function: int putenv (char *STRING)
Preliminary: | MT-Unsafe const:env | AS-Unsafe heap lock |
AC-Unsafe corrupt lock mem | *Note POSIX Safety Concepts::.
The 'putenv' function adds or removes definitions from the
environment. If the STRING is of the form 'NAME=VALUE', the
definition is added to the environment. Otherwise, the STRING is
interpreted as the name of an environment variable, and any
definition for this variable in the environment is removed.
If the function is successful it returns '0'. Otherwise the return
value is nonzero and 'errno' is set to indicate the error.
The difference to the 'setenv' function is that the exact string
given as the parameter STRING is put into the environment. If the
user should change the string after the 'putenv' call this will
reflect automatically in the environment. This also requires that
STRING not be an automatic variable whose scope is left before the
variable is removed from the environment. The same applies of
course to dynamically allocated variables which are freed later.
This function is part of the extended Unix interface. Since it was
also available in old SVID libraries you should define either
_XOPEN_SOURCE or _SVID_SOURCE before including any header.
-- Function: int setenv (const char *NAME, const char *VALUE, int
REPLACE)
Preliminary: | MT-Unsafe const:env | AS-Unsafe heap lock |
AC-Unsafe corrupt lock mem | *Note POSIX Safety Concepts::.
The 'setenv' function can be used to add a new definition to the
environment. The entry with the name NAME is replaced by the value
'NAME=VALUE'. Please note that this is also true if VALUE is the
empty string. To do this a new string is created and the strings
NAME and VALUE are copied. A null pointer for the VALUE parameter
is illegal. If the environment already contains an entry with key
NAME the REPLACE parameter controls the action. If replace is
zero, nothing happens. Otherwise the old entry is replaced by the
new one.
Please note that you cannot remove an entry completely using this
function.
If the function is successful it returns '0'. Otherwise the
environment is unchanged and the return value is '-1' and 'errno'
is set.
This function was originally part of the BSD library but is now
part of the Unix standard.
-- Function: int unsetenv (const char *NAME)
Preliminary: | MT-Unsafe const:env | AS-Unsafe lock | AC-Unsafe
lock | *Note POSIX Safety Concepts::.
Using this function one can remove an entry completely from the
environment. If the environment contains an entry with the key
NAME this whole entry is removed. A call to this function is
equivalent to a call to 'putenv' when the VALUE part of the string
is empty.
The function return '-1' if NAME is a null pointer, points to an
empty string, or points to a string containing a '=' character. It
returns '0' if the call succeeded.
This function was originally part of the BSD library but is now
part of the Unix standard. The BSD version had no return value,
though.
There is one more function to modify the whole environment. This
function is said to be used in the POSIX.9 (POSIX bindings for Fortran
77) and so one should expect it did made it into POSIX.1. But this
never happened. But we still provide this function as a GNU extension
to enable writing standard compliant Fortran environments.
-- Function: int clearenv (void)
Preliminary: | MT-Unsafe const:env | AS-Unsafe heap lock |
AC-Unsafe lock mem | *Note POSIX Safety Concepts::.
The 'clearenv' function removes all entries from the environment.
Using 'putenv' and 'setenv' new entries can be added again later.
If the function is successful it returns '0'. Otherwise the return
value is nonzero.
You can deal directly with the underlying representation of
environment objects to add more variables to the environment (for
example, to communicate with another program you are about to execute;
*note Executing a File::).
-- Variable: char ** environ
The environment is represented as an array of strings. Each string
is of the format 'NAME=VALUE'. The order in which strings appear
in the environment is not significant, but the same NAME must not
appear more than once. The last element of the array is a null
pointer.
This variable is declared in the header file 'unistd.h'.
If you just want to get the value of an environment variable, use
'getenv'.
Unix systems, and GNU systems, pass the initial value of 'environ' as
the third argument to 'main'. *Note Program Arguments::.

File: libc.info, Node: Standard Environment, Prev: Environment Access, Up: Environment Variables
25.4.2 Standard Environment Variables
-------------------------------------
These environment variables have standard meanings. This doesn't mean
that they are always present in the environment; but if these variables
_are_ present, they have these meanings. You shouldn't try to use these
environment variable names for some other purpose.
'HOME'
This is a string representing the user's "home directory", or
initial default working directory.
The user can set 'HOME' to any value. If you need to make sure to
obtain the proper home directory for a particular user, you should
not use 'HOME'; instead, look up the user's name in the user
database (*note User Database::).
For most purposes, it is better to use 'HOME', precisely because
this lets the user specify the value.
'LOGNAME'
This is the name that the user used to log in. Since the value in
the environment can be tweaked arbitrarily, this is not a reliable
way to identify the user who is running a program; a function like
'getlogin' (*note Who Logged In::) is better for that purpose.
For most purposes, it is better to use 'LOGNAME', precisely because
this lets the user specify the value.
'PATH'
A "path" is a sequence of directory names which is used for
searching for a file. The variable 'PATH' holds a path used for
searching for programs to be run.
The 'execlp' and 'execvp' functions (*note Executing a File::) use
this environment variable, as do many shells and other utilities
which are implemented in terms of those functions.
The syntax of a path is a sequence of directory names separated by
colons. An empty string instead of a directory name stands for the
current directory (*note Working Directory::).
A typical value for this environment variable might be a string
like:
:/bin:/etc:/usr/bin:/usr/new/X11:/usr/new:/usr/local/bin
This means that if the user tries to execute a program named 'foo',
the system will look for files named 'foo', '/bin/foo', '/etc/foo',
and so on. The first of these files that exists is the one that is
executed.
'TERM'
This specifies the kind of terminal that is receiving program
output. Some programs can make use of this information to take
advantage of special escape sequences or terminal modes supported
by particular kinds of terminals. Many programs which use the
termcap library (*note Find: (termcap)Finding a Terminal
Description.) use the 'TERM' environment variable, for example.
'TZ'
This specifies the time zone. *Note TZ Variable::, for information
about the format of this string and how it is used.
'LANG'
This specifies the default locale to use for attribute categories
where neither 'LC_ALL' nor the specific environment variable for
that category is set. *Note Locales::, for more information about
locales.
'LC_ALL'
If this environment variable is set it overrides the selection for
all the locales done using the other 'LC_*' environment variables.
The value of the other 'LC_*' environment variables is simply
ignored in this case.
'LC_COLLATE'
This specifies what locale to use for string sorting.
'LC_CTYPE'
This specifies what locale to use for character sets and character
classification.
'LC_MESSAGES'
This specifies what locale to use for printing messages and to
parse responses.
'LC_MONETARY'
This specifies what locale to use for formatting monetary values.
'LC_NUMERIC'
This specifies what locale to use for formatting numbers.
'LC_TIME'
This specifies what locale to use for formatting date/time values.
'NLSPATH'
This specifies the directories in which the 'catopen' function
looks for message translation catalogs.
'_POSIX_OPTION_ORDER'
If this environment variable is defined, it suppresses the usual
reordering of command line arguments by 'getopt' and 'argp_parse'.
*Note Argument Syntax::.

File: libc.info, Node: Auxiliary Vector, Next: System Calls, Prev: Environment Variables, Up: Program Basics
25.5 Auxiliary Vector
=====================
When a program is executed, it receives information from the operating
system about the environment in which it is operating. The form of this
information is a table of key-value pairs, where the keys are from the
set of 'AT_' values in 'elf.h'. Some of the data is provided by the
kernel for libc consumption, and may be obtained by ordinary interfaces,
such as 'sysconf'. However, on a platform-by-platform basis there may
be information that is not available any other way.
25.5.1 Definition of 'getauxval'
--------------------------------
-- Function: unsigned long int getauxval (unsigned long int TYPE)
Preliminary: | MT-Safe | AS-Safe | AC-Safe | *Note POSIX Safety
Concepts::.
This function is used to inquire about the entries in the auxiliary
vector. The TYPE argument should be one of the 'AT_' symbols
defined in 'elf.h'. If a matching entry is found, the value is
returned; if the entry is not found, zero is returned and 'errno'
is set to 'ENOENT'.
For some platforms, the key 'AT_HWCAP' is the easiest way to inquire
about any instruction set extensions available at runtime. In this
case, there will (of necessity) be a platform-specific set of 'HWCAP_'
values masked together that describe the capabilities of the cpu on
which the program is being executed.

File: libc.info, Node: System Calls, Next: Program Termination, Prev: Auxiliary Vector, Up: Program Basics
25.6 System Calls
=================
A system call is a request for service that a program makes of the
kernel. The service is generally something that only the kernel has the
privilege to do, such as doing I/O. Programmers don't normally need to
be concerned with system calls because there are functions in the GNU C
Library to do virtually everything that system calls do. These
functions work by making system calls themselves. For example, there is
a system call that changes the permissions of a file, but you don't need
to know about it because you can just use the GNU C Library's 'chmod'
function.
System calls are sometimes called kernel calls.
However, there are times when you want to make a system call
explicitly, and for that, the GNU C Library provides the 'syscall'
function. 'syscall' is harder to use and less portable than functions
like 'chmod', but easier and more portable than coding the system call
in assembler instructions.
'syscall' is most useful when you are working with a system call
which is special to your system or is newer than the GNU C Library you
are using. 'syscall' is implemented in an entirely generic way; the
function does not know anything about what a particular system call does
or even if it is valid.
The description of 'syscall' in this section assumes a certain
protocol for system calls on the various platforms on which the GNU C
Library runs. That protocol is not defined by any strong authority, but
we won't describe it here either because anyone who is coding 'syscall'
probably won't accept anything less than kernel and C library source
code as a specification of the interface between them anyway.
'syscall' is declared in 'unistd.h'.
-- Function: long int syscall (long int SYSNO, ...)
Preliminary: | MT-Safe | AS-Safe | AC-Safe | *Note POSIX Safety
Concepts::.
'syscall' performs a generic system call.
SYSNO is the system call number. Each kind of system call is
identified by a number. Macros for all the possible system call
numbers are defined in 'sys/syscall.h'
The remaining arguments are the arguments for the system call, in
order, and their meanings depend on the kind of system call. Each
kind of system call has a definite number of arguments, from zero
to five. If you code more arguments than the system call takes,
the extra ones to the right are ignored.
The return value is the return value from the system call, unless
the system call failed. In that case, 'syscall' returns '-1' and
sets 'errno' to an error code that the system call returned. Note
that system calls do not return '-1' when they succeed.
If you specify an invalid SYSNO, 'syscall' returns '-1' with
'errno' = 'ENOSYS'.
Example:
#include <unistd.h>
#include <sys/syscall.h>
#include <errno.h>
...
int rc;
rc = syscall(SYS_chmod, "/etc/passwd", 0444);
if (rc == -1)
fprintf(stderr, "chmod failed, errno = %d\n", errno);
This, if all the compatibility stars are aligned, is equivalent to
the following preferable code:
#include <sys/types.h>
#include <sys/stat.h>
#include <errno.h>
...
int rc;
rc = chmod("/etc/passwd", 0444);
if (rc == -1)
fprintf(stderr, "chmod failed, errno = %d\n", errno);

File: libc.info, Node: Program Termination, Prev: System Calls, Up: Program Basics
25.7 Program Termination
========================
The usual way for a program to terminate is simply for its 'main'
function to return. The "exit status value" returned from the 'main'
function is used to report information back to the process's parent
process or shell.
A program can also terminate normally by calling the 'exit' function.
In addition, programs can be terminated by signals; this is discussed
in more detail in *note Signal Handling::. The 'abort' function causes
a signal that kills the program.
* Menu:
* Normal Termination:: If a program calls 'exit', a
process terminates normally.
* Exit Status:: The 'exit status' provides information
about why the process terminated.
* Cleanups on Exit:: A process can run its own cleanup
functions upon normal termination.
* Aborting a Program:: The 'abort' function causes
abnormal program termination.
* Termination Internals:: What happens when a process terminates.

File: libc.info, Node: Normal Termination, Next: Exit Status, Up: Program Termination
25.7.1 Normal Termination
-------------------------
A process terminates normally when its program signals it is done by
calling 'exit'. Returning from 'main' is equivalent to calling 'exit',
and the value that 'main' returns is used as the argument to 'exit'.
-- Function: void exit (int STATUS)
Preliminary: | MT-Unsafe race:exit | AS-Unsafe corrupt | AC-Unsafe
corrupt lock | *Note POSIX Safety Concepts::.
The 'exit' function tells the system that the program is done,
which causes it to terminate the process.
STATUS is the program's exit status, which becomes part of the
process' termination status. This function does not return.
Normal termination causes the following actions:
1. Functions that were registered with the 'atexit' or 'on_exit'
functions are called in the reverse order of their registration.
This mechanism allows your application to specify its own "cleanup"
actions to be performed at program termination. Typically, this is
used to do things like saving program state information in a file,
or unlocking locks in shared data bases.
2. All open streams are closed, writing out any buffered output data.
See *note Closing Streams::. In addition, temporary files opened
with the 'tmpfile' function are removed; see *note Temporary
Files::.
3. '_exit' is called, terminating the program. *Note Termination
Internals::.

File: libc.info, Node: Exit Status, Next: Cleanups on Exit, Prev: Normal Termination, Up: Program Termination
25.7.2 Exit Status
------------------
When a program exits, it can return to the parent process a small amount
of information about the cause of termination, using the "exit status".
This is a value between 0 and 255 that the exiting process passes as an
argument to 'exit'.
Normally you should use the exit status to report very broad
information about success or failure. You can't provide a lot of detail
about the reasons for the failure, and most parent processes would not
want much detail anyway.
There are conventions for what sorts of status values certain
programs should return. The most common convention is simply 0 for
success and 1 for failure. Programs that perform comparison use a
different convention: they use status 1 to indicate a mismatch, and
status 2 to indicate an inability to compare. Your program should
follow an existing convention if an existing convention makes sense for
it.
A general convention reserves status values 128 and up for special
purposes. In particular, the value 128 is used to indicate failure to
execute another program in a subprocess. This convention is not
universally obeyed, but it is a good idea to follow it in your programs.
*Warning:* Don't try to use the number of errors as the exit status.
This is actually not very useful; a parent process would generally not
care how many errors occurred. Worse than that, it does not work,
because the status value is truncated to eight bits. Thus, if the
program tried to report 256 errors, the parent would receive a report of
0 errors--that is, success.
For the same reason, it does not work to use the value of 'errno' as
the exit status--these can exceed 255.
*Portability note:* Some non-POSIX systems use different conventions
for exit status values. For greater portability, you can use the macros
'EXIT_SUCCESS' and 'EXIT_FAILURE' for the conventional status value for
success and failure, respectively. They are declared in the file
'stdlib.h'.
-- Macro: int EXIT_SUCCESS
This macro can be used with the 'exit' function to indicate
successful program completion.
On POSIX systems, the value of this macro is '0'. On other
systems, the value might be some other (possibly non-constant)
integer expression.
-- Macro: int EXIT_FAILURE
This macro can be used with the 'exit' function to indicate
unsuccessful program completion in a general sense.
On POSIX systems, the value of this macro is '1'. On other
systems, the value might be some other (possibly non-constant)
integer expression. Other nonzero status values also indicate
failures. Certain programs use different nonzero status values to
indicate particular kinds of "non-success". For example, 'diff'
uses status value '1' to mean that the files are different, and '2'
or more to mean that there was difficulty in opening the files.
Don't confuse a program's exit status with a process' termination
status. There are lots of ways a process can terminate besides having
its program finish. In the event that the process termination _is_
caused by program termination (i.e., 'exit'), though, the program's exit
status becomes part of the process' termination status.

File: libc.info, Node: Cleanups on Exit, Next: Aborting a Program, Prev: Exit Status, Up: Program Termination
25.7.3 Cleanups on Exit
-----------------------
Your program can arrange to run its own cleanup functions if normal
termination happens. If you are writing a library for use in various
application programs, then it is unreliable to insist that all
applications call the library's cleanup functions explicitly before
exiting. It is much more robust to make the cleanup invisible to the
application, by setting up a cleanup function in the library itself
using 'atexit' or 'on_exit'.
-- Function: int atexit (void (*FUNCTION) (void))
Preliminary: | MT-Safe | AS-Unsafe heap lock | AC-Unsafe lock mem |
*Note POSIX Safety Concepts::.
The 'atexit' function registers the function FUNCTION to be called
at normal program termination. The FUNCTION is called with no
arguments.
The return value from 'atexit' is zero on success and nonzero if
the function cannot be registered.
-- Function: int on_exit (void (*FUNCTION)(int STATUS, void *ARG), void
*ARG)
Preliminary: | MT-Safe | AS-Unsafe heap lock | AC-Unsafe lock mem |
*Note POSIX Safety Concepts::.
This function is a somewhat more powerful variant of 'atexit'. It
accepts two arguments, a function FUNCTION and an arbitrary pointer
ARG. At normal program termination, the FUNCTION is called with
two arguments: the STATUS value passed to 'exit', and the ARG.
This function is included in the GNU C Library only for
compatibility for SunOS, and may not be supported by other
implementations.
Here's a trivial program that illustrates the use of 'exit' and
'atexit':
#include <stdio.h>
#include <stdlib.h>
void
bye (void)
{
puts ("Goodbye, cruel world....");
}
int
main (void)
{
atexit (bye);
exit (EXIT_SUCCESS);
}
When this program is executed, it just prints the message and exits.

File: libc.info, Node: Aborting a Program, Next: Termination Internals, Prev: Cleanups on Exit, Up: Program Termination
25.7.4 Aborting a Program
-------------------------
You can abort your program using the 'abort' function. The prototype
for this function is in 'stdlib.h'.
-- Function: void abort (void)
Preliminary: | MT-Safe | AS-Unsafe corrupt | AC-Unsafe lock corrupt
| *Note POSIX Safety Concepts::.
The 'abort' function causes abnormal program termination. This
does not execute cleanup functions registered with 'atexit' or
'on_exit'.
This function actually terminates the process by raising a
'SIGABRT' signal, and your program can include a handler to
intercept this signal; see *note Signal Handling::.
*Future Change Warning:* Proposed Federal censorship regulations may
prohibit us from giving you information about the possibility of calling
this function. We would be required to say that this is not an
acceptable way of terminating a program.

File: libc.info, Node: Termination Internals, Prev: Aborting a Program, Up: Program Termination
25.7.5 Termination Internals
----------------------------
The '_exit' function is the primitive used for process termination by
'exit'. It is declared in the header file 'unistd.h'.
-- Function: void _exit (int STATUS)
Preliminary: | MT-Safe | AS-Safe | AC-Safe | *Note POSIX Safety
Concepts::.
The '_exit' function is the primitive for causing a process to
terminate with status STATUS. Calling this function does not
execute cleanup functions registered with 'atexit' or 'on_exit'.
-- Function: void _Exit (int STATUS)
Preliminary: | MT-Safe | AS-Safe | AC-Safe | *Note POSIX Safety
Concepts::.
The '_Exit' function is the ISO C equivalent to '_exit'. The ISO C
committee members were not sure whether the definitions of '_exit'
and '_Exit' were compatible so they have not used the POSIX name.
This function was introduced in ISO C99 and is declared in
'stdlib.h'.
When a process terminates for any reason--either because the program
terminates, or as a result of a signal--the following things happen:
* All open file descriptors in the process are closed. *Note
Low-Level I/O::. Note that streams are not flushed automatically
when the process terminates; see *note I/O on Streams::.
* A process exit status is saved to be reported back to the parent
process via 'wait' or 'waitpid'; see *note Process Completion::.
If the program exited, this status includes as its low-order 8 bits
the program exit status.
* Any child processes of the process being terminated are assigned a
new parent process. (On most systems, including GNU, this is the
'init' process, with process ID 1.)
* A 'SIGCHLD' signal is sent to the parent process.
* If the process is a session leader that has a controlling terminal,
then a 'SIGHUP' signal is sent to each process in the foreground
job, and the controlling terminal is disassociated from that
session. *Note Job Control::.
* If termination of a process causes a process group to become
orphaned, and any member of that process group is stopped, then a
'SIGHUP' signal and a 'SIGCONT' signal are sent to each process in
the group. *Note Job Control::.

File: libc.info, Node: Processes, Next: Job Control, Prev: Program Basics, Up: Top
26 Processes
************
"Processes" are the primitive units for allocation of system resources.
Each process has its own address space and (usually) one thread of
control. A process executes a program; you can have multiple processes
executing the same program, but each process has its own copy of the
program within its own address space and executes it independently of
the other copies.
Processes are organized hierarchically. Each process has a "parent
process" which explicitly arranged to create it. The processes created
by a given parent are called its "child processes". A child inherits
many of its attributes from the parent process.
This chapter describes how a program can create, terminate, and
control child processes. Actually, there are three distinct operations
involved: creating a new child process, causing the new process to
execute a program, and coordinating the completion of the child process
with the original program.
The 'system' function provides a simple, portable mechanism for
running another program; it does all three steps automatically. If you
need more control over the details of how this is done, you can use the
primitive functions to do each step individually instead.
* Menu:
* Running a Command:: The easy way to run another program.
* Process Creation Concepts:: An overview of the hard way to do it.
* Process Identification:: How to get the process ID of a process.
* Creating a Process:: How to fork a child process.
* Executing a File:: How to make a process execute another program.
* Process Completion:: How to tell when a child process has completed.
* Process Completion Status:: How to interpret the status value
returned from a child process.
* BSD Wait Functions:: More functions, for backward compatibility.
* Process Creation Example:: A complete example program.

File: libc.info, Node: Running a Command, Next: Process Creation Concepts, Up: Processes
26.1 Running a Command
======================
The easy way to run another program is to use the 'system' function.
This function does all the work of running a subprogram, but it doesn't
give you much control over the details: you have to wait until the
subprogram terminates before you can do anything else.
-- Function: int system (const char *COMMAND)
Preliminary: | MT-Safe | AS-Unsafe plugin heap lock | AC-Unsafe
lock mem | *Note POSIX Safety Concepts::.
This function executes COMMAND as a shell command. In the GNU C
Library, it always uses the default shell 'sh' to run the command.
In particular, it searches the directories in 'PATH' to find
programs to execute. The return value is '-1' if it wasn't
possible to create the shell process, and otherwise is the status
of the shell process. *Note Process Completion::, for details on
how this status code can be interpreted.
If the COMMAND argument is a null pointer, a return value of zero
indicates that no command processor is available.
This function is a cancellation point in multi-threaded programs.
This is a problem if the thread allocates some resources (like
memory, file descriptors, semaphores or whatever) at the time
'system' is called. If the thread gets canceled these resources
stay allocated until the program ends. To avoid this calls to
'system' should be protected using cancellation handlers.
The 'system' function is declared in the header file 'stdlib.h'.
*Portability Note:* Some C implementations may not have any notion of
a command processor that can execute other programs. You can determine
whether a command processor exists by executing 'system (NULL)'; if the
return value is nonzero, a command processor is available.
The 'popen' and 'pclose' functions (*note Pipe to a Subprocess::) are
closely related to the 'system' function. They allow the parent process
to communicate with the standard input and output channels of the
command being executed.

File: libc.info, Node: Process Creation Concepts, Next: Process Identification, Prev: Running a Command, Up: Processes
26.2 Process Creation Concepts
==============================
This section gives an overview of processes and of the steps involved in
creating a process and making it run another program.
Each process is named by a "process ID" number. A unique process ID
is allocated to each process when it is created. The "lifetime" of a
process ends when its termination is reported to its parent process; at
that time, all of the process resources, including its process ID, are
freed.
Processes are created with the 'fork' system call (so the operation
of creating a new process is sometimes called "forking" a process). The
"child process" created by 'fork' is a copy of the original "parent
process", except that it has its own process ID.
After forking a child process, both the parent and child processes
continue to execute normally. If you want your program to wait for a
child process to finish executing before continuing, you must do this
explicitly after the fork operation, by calling 'wait' or 'waitpid'
(*note Process Completion::). These functions give you limited
information about why the child terminated--for example, its exit status
code.
A newly forked child process continues to execute the same program as
its parent process, at the point where the 'fork' call returns. You can
use the return value from 'fork' to tell whether the program is running
in the parent process or the child.
Having several processes run the same program is only occasionally
useful. But the child can execute another program using one of the
'exec' functions; see *note Executing a File::. The program that the
process is executing is called its "process image". Starting execution
of a new program causes the process to forget all about its previous
process image; when the new program exits, the process exits too,
instead of returning to the previous process image.

File: libc.info, Node: Process Identification, Next: Creating a Process, Prev: Process Creation Concepts, Up: Processes
26.3 Process Identification
===========================
The 'pid_t' data type represents process IDs. You can get the process
ID of a process by calling 'getpid'. The function 'getppid' returns the
process ID of the parent of the current process (this is also known as
the "parent process ID"). Your program should include the header files
'unistd.h' and 'sys/types.h' to use these functions.
-- Data Type: pid_t
The 'pid_t' data type is a signed integer type which is capable of
representing a process ID. In the GNU C Library, this is an 'int'.
-- Function: pid_t getpid (void)
Preliminary: | MT-Safe | AS-Safe | AC-Safe | *Note POSIX Safety
Concepts::.
The 'getpid' function returns the process ID of the current
process.
-- Function: pid_t getppid (void)
Preliminary: | MT-Safe | AS-Safe | AC-Safe | *Note POSIX Safety
Concepts::.
The 'getppid' function returns the process ID of the parent of the
current process.

File: libc.info, Node: Creating a Process, Next: Executing a File, Prev: Process Identification, Up: Processes
26.4 Creating a Process
=======================
The 'fork' function is the primitive for creating a process. It is
declared in the header file 'unistd.h'.
-- Function: pid_t fork (void)
Preliminary: | MT-Safe | AS-Unsafe plugin | AC-Unsafe lock | *Note
POSIX Safety Concepts::.
The 'fork' function creates a new process.
If the operation is successful, there are then both parent and
child processes and both see 'fork' return, but with different
values: it returns a value of '0' in the child process and returns
the child's process ID in the parent process.
If process creation failed, 'fork' returns a value of '-1' in the
parent process. The following 'errno' error conditions are defined
for 'fork':
'EAGAIN'
There aren't enough system resources to create another
process, or the user already has too many processes running.
This means exceeding the 'RLIMIT_NPROC' resource limit, which
can usually be increased; *note Limits on Resources::.
'ENOMEM'
The process requires more space than the system can supply.
The specific attributes of the child process that differ from the
parent process are:
* The child process has its own unique process ID.
* The parent process ID of the child process is the process ID of its
parent process.
* The child process gets its own copies of the parent process's open
file descriptors. Subsequently changing attributes of the file
descriptors in the parent process won't affect the file descriptors
in the child, and vice versa. *Note Control Operations::.
However, the file position associated with each descriptor is
shared by both processes; *note File Position::.
* The elapsed processor times for the child process are set to zero;
see *note Processor Time::.
* The child doesn't inherit file locks set by the parent process.
*Note Control Operations::.
* The child doesn't inherit alarms set by the parent process. *Note
Setting an Alarm::.
* The set of pending signals (*note Delivery of Signal::) for the
child process is cleared. (The child process inherits its mask of
blocked signals and signal actions from the parent process.)
-- Function: pid_t vfork (void)
Preliminary: | MT-Safe | AS-Unsafe plugin | AC-Unsafe lock | *Note
POSIX Safety Concepts::.
The 'vfork' function is similar to 'fork' but on some systems it is
more efficient; however, there are restrictions you must follow to
use it safely.
While 'fork' makes a complete copy of the calling process's address
space and allows both the parent and child to execute
independently, 'vfork' does not make this copy. Instead, the child
process created with 'vfork' shares its parent's address space
until it calls '_exit' or one of the 'exec' functions. In the
meantime, the parent process suspends execution.
You must be very careful not to allow the child process created
with 'vfork' to modify any global data or even local variables
shared with the parent. Furthermore, the child process cannot
return from (or do a long jump out of) the function that called
'vfork'! This would leave the parent process's control information
very confused. If in doubt, use 'fork' instead.
Some operating systems don't really implement 'vfork'. The GNU C
Library permits you to use 'vfork' on all systems, but actually
executes 'fork' if 'vfork' isn't available. If you follow the
proper precautions for using 'vfork', your program will still work
even if the system uses 'fork' instead.

File: libc.info, Node: Executing a File, Next: Process Completion, Prev: Creating a Process, Up: Processes
26.5 Executing a File
=====================
This section describes the 'exec' family of functions, for executing a
file as a process image. You can use these functions to make a child
process execute a new program after it has been forked.
To see the effects of 'exec' from the point of view of the called
program, see *note Program Basics::.
The functions in this family differ in how you specify the arguments,
but otherwise they all do the same thing. They are declared in the
header file 'unistd.h'.
-- Function: int execv (const char *FILENAME, char *const ARGV[])
Preliminary: | MT-Safe | AS-Safe | AC-Safe | *Note POSIX Safety
Concepts::.
The 'execv' function executes the file named by FILENAME as a new
process image.
The ARGV argument is an array of null-terminated strings that is
used to provide a value for the 'argv' argument to the 'main'
function of the program to be executed. The last element of this
array must be a null pointer. By convention, the first element of
this array is the file name of the program sans directory names.
*Note Program Arguments::, for full details on how programs can
access these arguments.
The environment for the new process image is taken from the
'environ' variable of the current process image; see *note
Environment Variables::, for information about environments.
-- Function: int execl (const char *FILENAME, const char *ARG0, ...)
Preliminary: | MT-Safe | AS-Unsafe heap | AC-Unsafe mem | *Note
POSIX Safety Concepts::.
This is similar to 'execv', but the ARGV strings are specified
individually instead of as an array. A null pointer must be passed
as the last such argument.
-- Function: int execve (const char *FILENAME, char *const ARGV[], char
*const ENV[])
Preliminary: | MT-Safe | AS-Safe | AC-Safe | *Note POSIX Safety
Concepts::.
This is similar to 'execv', but permits you to specify the
environment for the new program explicitly as the ENV argument.
This should be an array of strings in the same format as for the
'environ' variable; see *note Environment Access::.
-- Function: int execle (const char *FILENAME, const char *ARG0, ...,
char *const ENV[])
Preliminary: | MT-Safe | AS-Unsafe heap | AC-Unsafe mem | *Note
POSIX Safety Concepts::.
This is similar to 'execl', but permits you to specify the
environment for the new program explicitly. The environment
argument is passed following the null pointer that marks the last
ARGV argument, and should be an array of strings in the same format
as for the 'environ' variable.
-- Function: int execvp (const char *FILENAME, char *const ARGV[])
Preliminary: | MT-Safe env | AS-Unsafe heap | AC-Unsafe mem | *Note
POSIX Safety Concepts::.
The 'execvp' function is similar to 'execv', except that it
searches the directories listed in the 'PATH' environment variable
(*note Standard Environment::) to find the full file name of a file
from FILENAME if FILENAME does not contain a slash.
This function is useful for executing system utility programs,
because it looks for them in the places that the user has chosen.
Shells use it to run the commands that users type.
-- Function: int execlp (const char *FILENAME, const char *ARG0, ...)
Preliminary: | MT-Safe env | AS-Unsafe heap | AC-Unsafe mem | *Note
POSIX Safety Concepts::.
This function is like 'execl', except that it performs the same
file name searching as the 'execvp' function.
The size of the argument list and environment list taken together
must not be greater than 'ARG_MAX' bytes. *Note General Limits::. On
GNU/Hurd systems, the size (which compares against 'ARG_MAX') includes,
for each string, the number of characters in the string, plus the size
of a 'char *', plus one, rounded up to a multiple of the size of a 'char
*'. Other systems may have somewhat different rules for counting.
These functions normally don't return, since execution of a new
program causes the currently executing program to go away completely. A
value of '-1' is returned in the event of a failure. In addition to the
usual file name errors (*note File Name Errors::), the following 'errno'
error conditions are defined for these functions:
'E2BIG'
The combined size of the new program's argument list and
environment list is larger than 'ARG_MAX' bytes. GNU/Hurd systems
have no specific limit on the argument list size, so this error
code cannot result, but you may get 'ENOMEM' instead if the
arguments are too big for available memory.
'ENOEXEC'
The specified file can't be executed because it isn't in the right
format.
'ENOMEM'
Executing the specified file requires more storage than is
available.
If execution of the new file succeeds, it updates the access time
field of the file as if the file had been read. *Note File Times::, for
more details about access times of files.
The point at which the file is closed again is not specified, but is
at some point before the process exits or before another process image
is executed.
Executing a new process image completely changes the contents of
memory, copying only the argument and environment strings to new
locations. But many other attributes of the process are unchanged:
* The process ID and the parent process ID. *Note Process Creation
Concepts::.
* Session and process group membership. *Note Concepts of Job
Control::.
* Real user ID and group ID, and supplementary group IDs. *Note
Process Persona::.
* Pending alarms. *Note Setting an Alarm::.
* Current working directory and root directory. *Note Working
Directory::. On GNU/Hurd systems, the root directory is not copied
when executing a setuid program; instead the system default root
directory is used for the new program.
* File mode creation mask. *Note Setting Permissions::.
* Process signal mask; see *note Process Signal Mask::.
* Pending signals; see *note Blocking Signals::.
* Elapsed processor time associated with the process; see *note
Processor Time::.
If the set-user-ID and set-group-ID mode bits of the process image
file are set, this affects the effective user ID and effective group ID
(respectively) of the process. These concepts are discussed in detail
in *note Process Persona::.
Signals that are set to be ignored in the existing process image are
also set to be ignored in the new process image. All other signals are
set to the default action in the new process image. For more
information about signals, see *note Signal Handling::.
File descriptors open in the existing process image remain open in
the new process image, unless they have the 'FD_CLOEXEC' (close-on-exec)
flag set. The files that remain open inherit all attributes of the open
file description from the existing process image, including file locks.
File descriptors are discussed in *note Low-Level I/O::.
Streams, by contrast, cannot survive through 'exec' functions,
because they are located in the memory of the process itself. The new
process image has no streams except those it creates afresh. Each of
the streams in the pre-'exec' process image has a descriptor inside it,
and these descriptors do survive through 'exec' (provided that they do
not have 'FD_CLOEXEC' set). The new process image can reconnect these
to new streams using 'fdopen' (*note Descriptors and Streams::).

File: libc.info, Node: Process Completion, Next: Process Completion Status, Prev: Executing a File, Up: Processes
26.6 Process Completion
=======================
The functions described in this section are used to wait for a child
process to terminate or stop, and determine its status. These functions
are declared in the header file 'sys/wait.h'.
-- Function: pid_t waitpid (pid_t PID, int *STATUS-PTR, int OPTIONS)
Preliminary: | MT-Safe | AS-Safe | AC-Safe | *Note POSIX Safety
Concepts::.
The 'waitpid' function is used to request status information from a
child process whose process ID is PID. Normally, the calling
process is suspended until the child process makes status
information available by terminating.
Other values for the PID argument have special interpretations. A
value of '-1' or 'WAIT_ANY' requests status information for any
child process; a value of '0' or 'WAIT_MYPGRP' requests information
for any child process in the same process group as the calling
process; and any other negative value - PGID requests information
for any child process whose process group ID is PGID.
If status information for a child process is available immediately,
this function returns immediately without waiting. If more than
one eligible child process has status information available, one of
them is chosen randomly, and its status is returned immediately.
To get the status from the other eligible child processes, you need
to call 'waitpid' again.
The OPTIONS argument is a bit mask. Its value should be the
bitwise OR (that is, the '|' operator) of zero or more of the
'WNOHANG' and 'WUNTRACED' flags. You can use the 'WNOHANG' flag to
indicate that the parent process shouldn't wait; and the
'WUNTRACED' flag to request status information from stopped
processes as well as processes that have terminated.
The status information from the child process is stored in the
object that STATUS-PTR points to, unless STATUS-PTR is a null
pointer.
This function is a cancellation point in multi-threaded programs.
This is a problem if the thread allocates some resources (like
memory, file descriptors, semaphores or whatever) at the time
'waitpid' is called. If the thread gets canceled these resources
stay allocated until the program ends. To avoid this calls to
'waitpid' should be protected using cancellation handlers.
The return value is normally the process ID of the child process
whose status is reported. If there are child processes but none of
them is waiting to be noticed, 'waitpid' will block until one is.
However, if the 'WNOHANG' option was specified, 'waitpid' will
return zero instead of blocking.
If a specific PID to wait for was given to 'waitpid', it will
ignore all other children (if any). Therefore if there are
children waiting to be noticed but the child whose PID was
specified is not one of them, 'waitpid' will block or return zero
as described above.
A value of '-1' is returned in case of error. The following
'errno' error conditions are defined for this function:
'EINTR'
The function was interrupted by delivery of a signal to the
calling process. *Note Interrupted Primitives::.
'ECHILD'
There are no child processes to wait for, or the specified PID
is not a child of the calling process.
'EINVAL'
An invalid value was provided for the OPTIONS argument.
These symbolic constants are defined as values for the PID argument
to the 'waitpid' function.
'WAIT_ANY'
This constant macro (whose value is '-1') specifies that 'waitpid'
should return status information about any child process.
'WAIT_MYPGRP'
This constant (with value '0') specifies that 'waitpid' should
return status information about any child process in the same
process group as the calling process.
These symbolic constants are defined as flags for the OPTIONS
argument to the 'waitpid' function. You can bitwise-OR the flags
together to obtain a value to use as the argument.
'WNOHANG'
This flag specifies that 'waitpid' should return immediately
instead of waiting, if there is no child process ready to be
noticed.
'WUNTRACED'
This flag specifies that 'waitpid' should report the status of any
child processes that have been stopped as well as those that have
terminated.
-- Function: pid_t wait (int *STATUS-PTR)
Preliminary: | MT-Safe | AS-Safe | AC-Safe | *Note POSIX Safety
Concepts::.
This is a simplified version of 'waitpid', and is used to wait
until any one child process terminates. The call:
wait (&status)
is exactly equivalent to:
waitpid (-1, &status, 0)
This function is a cancellation point in multi-threaded programs.
This is a problem if the thread allocates some resources (like
memory, file descriptors, semaphores or whatever) at the time
'wait' is called. If the thread gets canceled these resources stay
allocated until the program ends. To avoid this calls to 'wait'
should be protected using cancellation handlers.
-- Function: pid_t wait4 (pid_t PID, int *STATUS-PTR, int OPTIONS,
struct rusage *USAGE)
Preliminary: | MT-Safe | AS-Safe | AC-Safe | *Note POSIX Safety
Concepts::.
If USAGE is a null pointer, 'wait4' is equivalent to 'waitpid (PID,
STATUS-PTR, OPTIONS)'.
If USAGE is not null, 'wait4' stores usage figures for the child
process in '*RUSAGE' (but only if the child has terminated, not if
it has stopped). *Note Resource Usage::.
This function is a BSD extension.
Here's an example of how to use 'waitpid' to get the status from all
child processes that have terminated, without ever waiting. This
function is designed to be a handler for 'SIGCHLD', the signal that
indicates that at least one child process has terminated.
void
sigchld_handler (int signum)
{
int pid, status, serrno;
serrno = errno;
while (1)
{
pid = waitpid (WAIT_ANY, &status, WNOHANG);
if (pid < 0)
{
perror ("waitpid");
break;
}
if (pid == 0)
break;
notice_termination (pid, status);
}
errno = serrno;
}

File: libc.info, Node: Process Completion Status, Next: BSD Wait Functions, Prev: Process Completion, Up: Processes
26.7 Process Completion Status
==============================
If the exit status value (*note Program Termination::) of the child
process is zero, then the status value reported by 'waitpid' or 'wait'
is also zero. You can test for other kinds of information encoded in
the returned status value using the following macros. These macros are
defined in the header file 'sys/wait.h'.
-- Macro: int WIFEXITED (int STATUS)
Preliminary: | MT-Safe | AS-Safe | AC-Safe | *Note POSIX Safety
Concepts::.
This macro returns a nonzero value if the child process terminated
normally with 'exit' or '_exit'.
-- Macro: int WEXITSTATUS (int STATUS)
Preliminary: | MT-Safe | AS-Safe | AC-Safe | *Note POSIX Safety
Concepts::.
If 'WIFEXITED' is true of STATUS, this macro returns the low-order
8 bits of the exit status value from the child process. *Note Exit
Status::.
-- Macro: int WIFSIGNALED (int STATUS)
Preliminary: | MT-Safe | AS-Safe | AC-Safe | *Note POSIX Safety
Concepts::.
This macro returns a nonzero value if the child process terminated
because it received a signal that was not handled. *Note Signal
Handling::.
-- Macro: int WTERMSIG (int STATUS)
Preliminary: | MT-Safe | AS-Safe | AC-Safe | *Note POSIX Safety
Concepts::.
If 'WIFSIGNALED' is true of STATUS, this macro returns the signal
number of the signal that terminated the child process.
-- Macro: int WCOREDUMP (int STATUS)
Preliminary: | MT-Safe | AS-Safe | AC-Safe | *Note POSIX Safety
Concepts::.
This macro returns a nonzero value if the child process terminated
and produced a core dump.
-- Macro: int WIFSTOPPED (int STATUS)
Preliminary: | MT-Safe | AS-Safe | AC-Safe | *Note POSIX Safety
Concepts::.
This macro returns a nonzero value if the child process is stopped.
-- Macro: int WSTOPSIG (int STATUS)
Preliminary: | MT-Safe | AS-Safe | AC-Safe | *Note POSIX Safety
Concepts::.
If 'WIFSTOPPED' is true of STATUS, this macro returns the signal
number of the signal that caused the child process to stop.

File: libc.info, Node: BSD Wait Functions, Next: Process Creation Example, Prev: Process Completion Status, Up: Processes
26.8 BSD Process Wait Functions
===============================
The GNU C Library also provides these related facilities for
compatibility with BSD Unix. BSD uses the 'union wait' data type to
represent status values rather than an 'int'. The two representations
are actually interchangeable; they describe the same bit patterns. The
GNU C Library defines macros such as 'WEXITSTATUS' so that they will
work on either kind of object, and the 'wait' function is defined to
accept either type of pointer as its STATUS-PTR argument.
These functions are declared in 'sys/wait.h'.
-- Data Type: union wait
This data type represents program termination status values. It
has the following members:
'int w_termsig'
The value of this member is the same as that of the 'WTERMSIG'
macro.
'int w_coredump'
The value of this member is the same as that of the
'WCOREDUMP' macro.
'int w_retcode'
The value of this member is the same as that of the
'WEXITSTATUS' macro.
'int w_stopsig'
The value of this member is the same as that of the 'WSTOPSIG'
macro.
Instead of accessing these members directly, you should use the
equivalent macros.
The 'wait3' function is the predecessor to 'wait4', which is more
flexible. 'wait3' is now obsolete.
-- Function: pid_t wait3 (union wait *STATUS-PTR, int OPTIONS, struct
rusage *USAGE)
Preliminary: | MT-Safe | AS-Safe | AC-Safe | *Note POSIX Safety
Concepts::.
If USAGE is a null pointer, 'wait3' is equivalent to 'waitpid (-1,
STATUS-PTR, OPTIONS)'.
If USAGE is not null, 'wait3' stores usage figures for the child
process in '*RUSAGE' (but only if the child has terminated, not if
it has stopped). *Note Resource Usage::.

File: libc.info, Node: Process Creation Example, Prev: BSD Wait Functions, Up: Processes
26.9 Process Creation Example
=============================
Here is an example program showing how you might write a function
similar to the built-in 'system'. It executes its COMMAND argument
using the equivalent of 'sh -c COMMAND'.
#include <stddef.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/wait.h>
/* Execute the command using this shell program. */
#define SHELL "/bin/sh"
int
my_system (const char *command)
{
int status;
pid_t pid;
pid = fork ();
if (pid == 0)
{
/* This is the child process. Execute the shell command. */
execl (SHELL, SHELL, "-c", command, NULL);
_exit (EXIT_FAILURE);
}
else if (pid < 0)
/* The fork failed. Report failure. */
status = -1;
else
/* This is the parent process. Wait for the child to complete. */
if (waitpid (pid, &status, 0) != pid)
status = -1;
return status;
}
There are a couple of things you should pay attention to in this
example.
Remember that the first 'argv' argument supplied to the program
represents the name of the program being executed. That is why, in the
call to 'execl', 'SHELL' is supplied once to name the program to execute
and a second time to supply a value for 'argv[0]'.
The 'execl' call in the child process doesn't return if it is
successful. If it fails, you must do something to make the child
process terminate. Just returning a bad status code with 'return' would
leave two processes running the original program. Instead, the right
behavior is for the child process to report failure to its parent
process.
Call '_exit' to accomplish this. The reason for using '_exit'
instead of 'exit' is to avoid flushing fully buffered streams such as
'stdout'. The buffers of these streams probably contain data that was
copied from the parent process by the 'fork', data that will be output
eventually by the parent process. Calling 'exit' in the child would
output the data twice. *Note Termination Internals::.

File: libc.info, Node: Job Control, Next: Name Service Switch, Prev: Processes, Up: Top
27 Job Control
**************
"Job control" refers to the protocol for allowing a user to move between
multiple "process groups" (or "jobs") within a single "login session".
The job control facilities are set up so that appropriate behavior for
most programs happens automatically and they need not do anything
special about job control. So you can probably ignore the material in
this chapter unless you are writing a shell or login program.
You need to be familiar with concepts relating to process creation
(*note Process Creation Concepts::) and signal handling (*note Signal
Handling::) in order to understand this material presented in this
chapter.
* Menu:
* Concepts of Job Control:: Jobs can be controlled by a shell.
* Job Control is Optional:: Not all POSIX systems support job control.
* Controlling Terminal:: How a process gets its controlling terminal.
* Access to the Terminal:: How processes share the controlling terminal.
* Orphaned Process Groups:: Jobs left after the user logs out.
* Implementing a Shell:: What a shell must do to implement job control.
* Functions for Job Control:: Functions to control process groups.

File: libc.info, Node: Concepts of Job Control, Next: Job Control is Optional, Up: Job Control
27.1 Concepts of Job Control
============================
The fundamental purpose of an interactive shell is to read commands from
the user's terminal and create processes to execute the programs
specified by those commands. It can do this using the 'fork' (*note
Creating a Process::) and 'exec' (*note Executing a File::) functions.
A single command may run just one process--but often one command uses
several processes. If you use the '|' operator in a shell command, you
explicitly request several programs in their own processes. But even if
you run just one program, it can use multiple processes internally. For
example, a single compilation command such as 'cc -c foo.c' typically
uses four processes (though normally only two at any given time). If
you run 'make', its job is to run other programs in separate processes.
The processes belonging to a single command are called a "process
group" or "job". This is so that you can operate on all of them at
once. For example, typing 'C-c' sends the signal 'SIGINT' to terminate
all the processes in the foreground process group.
A "session" is a larger group of processes. Normally all the
processes that stem from a single login belong to the same session.
Every process belongs to a process group. When a process is created,
it becomes a member of the same process group and session as its parent
process. You can put it in another process group using the 'setpgid'
function, provided the process group belongs to the same session.
The only way to put a process in a different session is to make it
the initial process of a new session, or a "session leader", using the
'setsid' function. This also puts the session leader into a new process
group, and you can't move it out of that process group again.
Usually, new sessions are created by the system login program, and
the session leader is the process running the user's login shell.
A shell that supports job control must arrange to control which job
can use the terminal at any time. Otherwise there might be multiple
jobs trying to read from the terminal at once, and confusion about which
process should receive the input typed by the user. To prevent this,
the shell must cooperate with the terminal driver using the protocol
described in this chapter.
The shell can give unlimited access to the controlling terminal to
only one process group at a time. This is called the "foreground job"
on that controlling terminal. Other process groups managed by the shell
that are executing without such access to the terminal are called
"background jobs".
If a background job needs to read from its controlling terminal, it
is "stopped" by the terminal driver; if the 'TOSTOP' mode is set,
likewise for writing. The user can stop a foreground job by typing the
SUSP character (*note Special Characters::) and a program can stop any
job by sending it a 'SIGSTOP' signal. It's the responsibility of the
shell to notice when jobs stop, to notify the user about them, and to
provide mechanisms for allowing the user to interactively continue
stopped jobs and switch jobs between foreground and background.
*Note Access to the Terminal::, for more information about I/O to the
controlling terminal,

File: libc.info, Node: Job Control is Optional, Next: Controlling Terminal, Prev: Concepts of Job Control, Up: Job Control
27.2 Job Control is Optional
============================
Not all operating systems support job control. GNU systems do support
job control, but if you are using the GNU C Library on some other
system, that system may not support job control itself.
You can use the '_POSIX_JOB_CONTROL' macro to test at compile-time
whether the system supports job control. *Note System Options::.
If job control is not supported, then there can be only one process
group per session, which behaves as if it were always in the foreground.
The functions for creating additional process groups simply fail with
the error code 'ENOSYS'.
The macros naming the various job control signals (*note Job Control
Signals::) are defined even if job control is not supported. However,
the system never generates these signals, and attempts to send a job
control signal or examine or specify their actions report errors or do
nothing.

File: libc.info, Node: Controlling Terminal, Next: Access to the Terminal, Prev: Job Control is Optional, Up: Job Control
27.3 Controlling Terminal of a Process
======================================
One of the attributes of a process is its controlling terminal. Child
processes created with 'fork' inherit the controlling terminal from
their parent process. In this way, all the processes in a session
inherit the controlling terminal from the session leader. A session
leader that has control of a terminal is called the "controlling
process" of that terminal.
You generally do not need to worry about the exact mechanism used to
allocate a controlling terminal to a session, since it is done for you
by the system when you log in.
An individual process disconnects from its controlling terminal when
it calls 'setsid' to become the leader of a new session. *Note Process
Group Functions::.

File: libc.info, Node: Access to the Terminal, Next: Orphaned Process Groups, Prev: Controlling Terminal, Up: Job Control
27.4 Access to the Controlling Terminal
=======================================
Processes in the foreground job of a controlling terminal have
unrestricted access to that terminal; background processes do not. This
section describes in more detail what happens when a process in a
background job tries to access its controlling terminal.
When a process in a background job tries to read from its controlling
terminal, the process group is usually sent a 'SIGTTIN' signal. This
normally causes all of the processes in that group to stop (unless they
handle the signal and don't stop themselves). However, if the reading
process is ignoring or blocking this signal, then 'read' fails with an
'EIO' error instead.
Similarly, when a process in a background job tries to write to its
controlling terminal, the default behavior is to send a 'SIGTTOU' signal
to the process group. However, the behavior is modified by the 'TOSTOP'
bit of the local modes flags (*note Local Modes::). If this bit is not
set (which is the default), then writing to the controlling terminal is
always permitted without sending a signal. Writing is also permitted if
the 'SIGTTOU' signal is being ignored or blocked by the writing process.
Most other terminal operations that a program can do are treated as
reading or as writing. (The description of each operation should say
which.)
For more information about the primitive 'read' and 'write'
functions, see *note I/O Primitives::.

File: libc.info, Node: Orphaned Process Groups, Next: Implementing a Shell, Prev: Access to the Terminal, Up: Job Control
27.5 Orphaned Process Groups
============================
When a controlling process terminates, its terminal becomes free and a
new session can be established on it. (In fact, another user could log
in on the terminal.) This could cause a problem if any processes from
the old session are still trying to use that terminal.
To prevent problems, process groups that continue running even after
the session leader has terminated are marked as "orphaned process
groups".
When a process group becomes an orphan, its processes are sent a
'SIGHUP' signal. Ordinarily, this causes the processes to terminate.
However, if a program ignores this signal or establishes a handler for
it (*note Signal Handling::), it can continue running as in the orphan
process group even after its controlling process terminates; but it
still cannot access the terminal any more.

File: libc.info, Node: Implementing a Shell, Next: Functions for Job Control, Prev: Orphaned Process Groups, Up: Job Control
27.6 Implementing a Job Control Shell
=====================================
This section describes what a shell must do to implement job control, by
presenting an extensive sample program to illustrate the concepts
involved.
* Menu:
* Data Structures:: Introduction to the sample shell.
* Initializing the Shell:: What the shell must do to take
responsibility for job control.
* Launching Jobs:: Creating jobs to execute commands.
* Foreground and Background:: Putting a job in foreground of background.
* Stopped and Terminated Jobs:: Reporting job status.
* Continuing Stopped Jobs:: How to continue a stopped job in
the foreground or background.
* Missing Pieces:: Other parts of the shell.

File: libc.info, Node: Data Structures, Next: Initializing the Shell, Up: Implementing a Shell
27.6.1 Data Structures for the Shell
------------------------------------
All of the program examples included in this chapter are part of a
simple shell program. This section presents data structures and utility
functions which are used throughout the example.
The sample shell deals mainly with two data structures. The 'job'
type contains information about a job, which is a set of subprocesses
linked together with pipes. The 'process' type holds information about
a single subprocess. Here are the relevant data structure declarations:
/* A process is a single process. */
typedef struct process
{
struct process *next; /* next process in pipeline */
char **argv; /* for exec */
pid_t pid; /* process ID */
char completed; /* true if process has completed */
char stopped; /* true if process has stopped */
int status; /* reported status value */
} process;
/* A job is a pipeline of processes. */
typedef struct job
{
struct job *next; /* next active job */
char *command; /* command line, used for messages */
process *first_process; /* list of processes in this job */
pid_t pgid; /* process group ID */
char notified; /* true if user told about stopped job */
struct termios tmodes; /* saved terminal modes */
int stdin, stdout, stderr; /* standard i/o channels */
} job;
/* The active jobs are linked into a list. This is its head. */
job *first_job = NULL;
Here are some utility functions that are used for operating on 'job'
objects.
/* Find the active job with the indicated PGID. */
job *
find_job (pid_t pgid)
{
job *j;
for (j = first_job; j; j = j->next)
if (j->pgid == pgid)
return j;
return NULL;
}
/* Return true if all processes in the job have stopped or completed. */
int
job_is_stopped (job *j)
{
process *p;
for (p = j->first_process; p; p = p->next)
if (!p->completed && !p->stopped)
return 0;
return 1;
}
/* Return true if all processes in the job have completed. */
int
job_is_completed (job *j)
{
process *p;
for (p = j->first_process; p; p = p->next)
if (!p->completed)
return 0;
return 1;
}

File: libc.info, Node: Initializing the Shell, Next: Launching Jobs, Prev: Data Structures, Up: Implementing a Shell
27.6.2 Initializing the Shell
-----------------------------
When a shell program that normally performs job control is started, it
has to be careful in case it has been invoked from another shell that is
already doing its own job control.
A subshell that runs interactively has to ensure that it has been
placed in the foreground by its parent shell before it can enable job
control itself. It does this by getting its initial process group ID
with the 'getpgrp' function, and comparing it to the process group ID of
the current foreground job associated with its controlling terminal
(which can be retrieved using the 'tcgetpgrp' function).
If the subshell is not running as a foreground job, it must stop
itself by sending a 'SIGTTIN' signal to its own process group. It may
not arbitrarily put itself into the foreground; it must wait for the
user to tell the parent shell to do this. If the subshell is continued
again, it should repeat the check and stop itself again if it is still
not in the foreground.
Once the subshell has been placed into the foreground by its parent
shell, it can enable its own job control. It does this by calling
'setpgid' to put itself into its own process group, and then calling
'tcsetpgrp' to place this process group into the foreground.
When a shell enables job control, it should set itself to ignore all
the job control stop signals so that it doesn't accidentally stop
itself. You can do this by setting the action for all the stop signals
to 'SIG_IGN'.