blob: ed376977e5a83a14a7b54b34a0eb06bf4d4c6c7e [file] [log] [blame]
This is /home/vagrant/rpmbuild/BUILD/build-eglibc/manual/,
produced by makeinfo version 4.13 from libc.texinfo.
INFO-DIR-SECTION Software libraries
* Libc: (libc). C library.
INFO-DIR-SECTION GNU C library functions and macros
* 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.
* 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.
* 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.
* 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_getattr_default_np: (libc)Default Thread Attributes.
* 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.
* 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.
This file documents the GNU C Library.
This is `The GNU C Library Reference Manual', for version
2.18-2013.10 (EGLIBC).
Copyright (C) 1993-2013 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."

File:, 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.
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.
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.
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
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.
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.
This specifies the time zone. *Note TZ Variable::, for
information about the format of this string and how it is used.
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
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.
This specifies what locale to use for string sorting.
This specifies what locale to use for character sets and character
This specifies what locale to use for printing messages and to
parse responses.
This specifies what locale to use for formatting monetary values.
This specifies what locale to use for formatting numbers.
This specifies what locale to use for formatting date/time values.
This specifies the directories in which the `catopen' function
looks for message translation catalogs.
If this environment variable is defined, it suppresses the usual
reordering of command line arguments by `getopt' and `argp_parse'.
*Note Argument Syntax::.

File:, 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)
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.
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:, 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, ...)
`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'.
#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:, 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:, 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)
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
3. `_exit' is called, terminating the program. *Note Termination

File:, 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
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:, 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))
The `atexit' function registers the function FUNCTION to be called
at normal program termination. The FUNCTION is called with no
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)
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
Here's a trivial program that illustrates the use of `exit' and
#include <stdio.h>
#include <stdlib.h>
bye (void)
puts ("Goodbye, cruel world....");
main (void)
atexit (bye);
When this program is executed, it just prints the message and exits.

File:, 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)
The `abort' function causes abnormal program termination. This
does not execute cleanup functions registered with `atexit' or
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:, 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)
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)
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
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:, 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:, 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)
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
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:, 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
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:, 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)
The `getpid' function returns the process ID of the current
-- Function: pid_t getppid (void)
The `getppid' function returns the process ID of the parent of the
current process.

File:, 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)
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':
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::.
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)
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:, 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[])
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, ...)
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[])
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[])
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[])
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, ...)
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:
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.
The specified file can't be executed because it isn't in the right
Executing the specified file requires more storage than is
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
* Session and process group membership. *Note Concepts of Job
* 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:, 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)
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
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:
The function was interrupted by delivery of a signal to the
calling process. *Note Interrupted Primitives::.
There are no child processes to wait for, or the specified PID
is not a child of the calling process.
An invalid value was provided for the OPTIONS argument.
These symbolic constants are defined as values for the PID argument
to the `waitpid' function.
This constant macro (whose value is `-1') specifies that `waitpid'
should return status information about any child process.
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.
This flag specifies that `waitpid' should return immediately
instead of waiting, if there is no child process ready to be
This flag specifies that `waitpid' should report the status of any
child processes that have been stopped as well as those that have
-- Function: pid_t wait (int *STATUS-PTR)
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)
If USAGE is a null pointer, `wait4' is equivalent to `waitpid
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.
sigchld_handler (int signum)
int pid, status, serrno;
serrno = errno;
while (1)
pid = waitpid (WAIT_ANY, &status, WNOHANG);
if (pid < 0)
perror ("waitpid");
if (pid == 0)
notice_termination (pid, status);
errno = serrno;

File:, 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)
This macro returns a nonzero value if the child process terminated
normally with `exit' or `_exit'.
-- Macro: int WEXITSTATUS (int STATUS)
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)
This macro returns a nonzero value if the child process terminated
because it received a signal that was not handled. *Note Signal
-- Macro: int WTERMSIG (int STATUS)
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)
This macro returns a nonzero value if the child process terminated
and produced a core dump.
-- Macro: int WIFSTOPPED (int STATUS)
This macro returns a nonzero value if the child process is stopped.
-- Macro: int WSTOPSIG (int STATUS)
If `WIFSTOPPED' is true of STATUS, this macro returns the signal
number of the signal that caused the child process to stop.

File:, 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
`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)
If USAGE is a null pointer, `wait3' is equivalent to `waitpid (-1,
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:, 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"
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);
else if (pid < 0)
/* The fork failed. Report failure. */
status = -1;
/* 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
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
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:, 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
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
* 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:, 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
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
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:, 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

File:, 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:, 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
For more information about the primitive `read' and `write'
functions, see *note I/O Primitives::.

File:, 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
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:, 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
* 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:, 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'
/* 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. */
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. */
job_is_completed (job *j)
process *p;
for (p = j->first_process; p; p = p->next)
if (!p->completed)
return 0;
return 1;

File:, 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'.
A subshell that runs non-interactively cannot and should not support
job control. It must leave all processes it creates in the same process
group as the shell itself; this allows the non-interactive shell and its
child processes to be treated as a single job by the parent shell. This
is easy to do--just don't use any of the job control primitives--but
you must remember to make the shell do it.
Here is the initialization code for the sample shell that shows how
to do all of this.
/* Keep track of attributes of the shell. */
#include <sys/types.h>
#include <termios.h>
#include <unistd.h>
pid_t shell_pgid;
struct termios shell_tmodes;
int shell_terminal;
int shell_is_interactive;
/* Make sure the shell is running interactively as the foreground job
before proceeding. */
init_shell ()
/* See if we are running interactively. */
shell_terminal = STDIN_FILENO;
shell_is_interactive = isatty (shell_terminal);
if (shell_is_interactive)
/* Loop until we are in the foreground. */
while (tcgetpgrp (shell_terminal) != (shell_pgid = getpgrp ()))
kill (- shell_pgid, SIGTTIN);
/* Ignore interactive and job-control signals. */
signal (SIGINT, SIG_IGN);
signal (SIGQUIT, SIG_IGN);
signal (SIGTSTP, SIG_IGN);
signal (SIGTTIN, SIG_IGN);
signal (SIGTTOU, SIG_IGN);
signal (SIGCHLD, SIG_IGN);
/* Put ourselves in our own process group. */
shell_pgid = getpid ();
if (setpgid (shell_pgid, shell_pgid) < 0)
perror ("Couldn't put the shell in its own process group");
exit (1);
/* Grab control of the terminal. */
tcsetpgrp (shell_terminal, shell_pgid);
/* Save default terminal attributes for shell. */
tcgetattr (shell_terminal, &shell_tmodes);

File:, Node: Launching Jobs, Next: Foreground and Background, Prev: Initializing the Shell, Up: Implementing a Shell
27.6.3 Launching Jobs
Once the shell has taken responsibility for performing job control on
its controlling terminal, it can launch jobs in response to commands
typed by the user.
To create the processes in a process group, you use the same `fork'
and `exec' functions described in *note Process Creation Concepts::.
Since there are multiple child processes involved, though, things are a
little more complicated and you must be careful to do things in the
right order. Otherwise, nasty race conditions can result.
You have two choices for how to structure the tree of parent-child
relationships among the processes. You can either make all the
processes in the process group be children of the shell process, or you
can make one process in group be the ancestor of all the other processes
in that group. The sample shell program presented in this chapter uses
the first approach because it makes bookkeeping somewhat simpler.
As each process is forked, it should put itself in the new process
group by calling `setpgid'; see *note Process Group Functions::. The
first process in the new group becomes its "process group leader", and
its process ID becomes the "process group ID" for the group.
The shell should also call `setpgid' to put each of its child
processes into the new process group. This is because there is a
potential timing problem: each child process must be put in the process
group before it begins executing a new program, and the shell depends on
having all the child processes in the group before it continues
executing. If both the child processes and the shell call `setpgid',
this ensures that the right things happen no matter which process gets
to it first.
If the job is being launched as a foreground job, the new process
group also needs to be put into the foreground on the controlling
terminal using `tcsetpgrp'. Again, this should be done by the shell as
well as by each of its child processes, to avoid race conditions.
The next thing each child process should do is to reset its signal
During initialization, the shell process set itself to ignore job
control signals; see *note Initializing the Shell::. As a result, any
child processes it creates also ignore these signals by inheritance.
This is definitely undesirable, so each child process should explicitly
set the actions for these signals back to `SIG_DFL' just after it is
Since shells follow this convention, applications can assume that
they inherit the correct handling of these signals from the parent
process. But every application has a responsibility not to mess up the
handling of stop signals. Applications that disable the normal
interpretation of the SUSP character should provide some other
mechanism for the user to stop the job. When the user invokes this
mechanism, the program should send a `SIGTSTP' signal to the process
group of the process, not just to the process itself. *Note Signaling
Another Process::.
Finally, each child process should call `exec' in the normal way.
This is also the point at which redirection of the standard input and
output channels should be handled. *Note Duplicating Descriptors::,
for an explanation of how to do this.
Here is the function from the sample shell program that is
responsible for launching a program. The function is executed by each
child process immediately after it has been forked by the shell, and
never returns.
launch_process (process *p, pid_t pgid,
int infile, int outfile, int errfile,
int foreground)
pid_t pid;
if (shell_is_interactive)
/* Put the process into the process group and give the process group
the terminal, if appropriate.
This has to be done both by the shell and in the individual
child processes because of potential race conditions. */
pid = getpid ();
if (pgid == 0) pgid = pid;
setpgid (pid, pgid);
if (foreground)
tcsetpgrp (shell_terminal, pgid);
/* Set the handling for job control signals back to the default. */
signal (SIGINT, SIG_DFL);
signal (SIGQUIT, SIG_DFL);
signal (SIGTSTP, SIG_DFL);
signal (SIGTTIN, SIG_DFL);
signal (SIGTTOU, SIG_DFL);
signal (SIGCHLD, SIG_DFL);
/* Set the standard input/output channels of the new process. */
if (infile != STDIN_FILENO)
dup2 (infile, STDIN_FILENO);
close (infile);
if (outfile != STDOUT_FILENO)
dup2 (outfile, STDOUT_FILENO);
close (outfile);
if (errfile != STDERR_FILENO)
dup2 (errfile, STDERR_FILENO);
close (errfile);
/* Exec the new process. Make sure we exit. */
execvp (p->argv[0], p->argv);
perror ("execvp");
exit (1);
If the shell is not running interactively, this function does not do
anything with process groups or signals. Remember that a shell not
performing job control must keep all of its subprocesses in the same
process group as the shell itself.
Next, here is the function that actually launches a complete job.
After creating the child processes, this function calls some other
functions to put the newly created job into the foreground or
background; these are discussed in *note Foreground and Background::.
launch_job (job *j, int foreground)
process *p;
pid_t pid;
int mypipe[2], infile, outfile;
infile = j->stdin;
for (p = j->first_process; p; p = p->next)
/* Set up pipes, if necessary. */
if (p->next)
if (pipe (mypipe) < 0)
perror ("pipe");
exit (1);
outfile = mypipe[1];
outfile = j->stdout;
/* Fork the child processes. */
pid = fork ();
if (pid == 0)
/* This is the child process. */
launch_process (p, j->pgid, infile,
outfile, j->stderr, foreground);
else if (pid < 0)
/* The fork failed. */
perror ("fork");
exit (1);
/* This is the parent process. */
p->pid = pid;
if (shell_is_interactive)
if (!j->pgid)
j->pgid = pid;
setpgid (pid, j->pgid);
/* Clean up after pipes. */
if (infile != j->stdin)
close (infile);
if (outfile != j->stdout)
close (outfile);
infile = mypipe[0];
format_job_info (j, "launched");
if (!shell_is_interactive)
wait_for_job (j);
else if (foreground)
put_job_in_foreground (j, 0);
put_job_in_background (j, 0);

File:, Node: Foreground and Background, Next: Stopped and Terminated Jobs, Prev: Launching Jobs, Up: Implementing a Shell
27.6.4 Foreground and Background
Now let's consider what actions must be taken by the shell when it
launches a job into the foreground, and how this differs from what must
be done when a background job is launched.
When a foreground job is launched, the shell must first give it
access to the controlling terminal by calling `tcsetpgrp'. Then, the
shell should wait for processes in that process group to terminate or
stop. This is discussed in more detail in *note Stopped and Terminated
When all of the processes in the group have either completed or
stopped, the shell should regain control of the terminal for its own
process group by calling `tcsetpgrp' again. Since stop signals caused
by I/O from a background process or a SUSP character typed by the user
are sent to the process group, normally all the processes in the job
stop together.
The foreground job may have left the terminal in a strange state, so
the shell should restore its own saved terminal modes before
continuing. In case the job is merely stopped, the shell should first
save the current terminal modes so that it can restore them later if
the job is continued. The functions for dealing with terminal modes are
`tcgetattr' and `tcsetattr'; these are described in *note Terminal
Here is the sample shell's function for doing all of this.
/* Put job J in the foreground. If CONT is nonzero,
restore the saved terminal modes and send the process group a
`SIGCONT' signal to wake it up before we block. */
put_job_in_foreground (job *j, int cont)
/* Put the job into the foreground. */
tcsetpgrp (shell_terminal, j->pgid);
/* Send the job a continue signal, if necessary. */
if (cont)
tcsetattr (shell_terminal, TCSADRAIN, &j->tmodes);
if (kill (- j->pgid, SIGCONT) < 0)
perror ("kill (SIGCONT)");
/* Wait for it to report. */
wait_for_job (j);
/* Put the shell back in the foreground. */
tcsetpgrp (shell_terminal, shell_pgid);
/* Restore the shell's terminal modes. */
tcgetattr (shell_terminal, &j->tmodes);
tcsetattr (shell_terminal, TCSADRAIN, &shell_tmodes);
If the process group is launched as a background job, the shell
should remain in the foreground itself and continue to read commands
from the terminal.
In the sample shell, there is not much that needs to be done to put
a job into the background. Here is the function it uses:
/* Put a job in the background. If the cont argument is true, send
the process group a `SIGCONT' signal to wake it up. */
put_job_in_background (job *j, int cont)
/* Send the job a continue signal, if necessary. */
if (cont)
if (kill (-j->pgid, SIGCONT) < 0)
perror ("kill (SIGCONT)");

File:, Node: Stopped and Terminated Jobs, Next: Continuing Stopped Jobs, Prev: Foreground and Background, Up: Implementing a Shell
27.6.5 Stopped and Terminated Jobs
When a foreground process is launched, the shell must block until all of
the processes in that job have either terminated or stopped. It can do
this by calling the `waitpid' function; see *note Process Completion::.
Use the `WUNTRACED' option so that status is reported for processes
that stop as well as processes that terminate.
The shell must also check on the status of background jobs so that it
can report terminated and stopped jobs to the user; this can be done by
calling `waitpid' with the `WNOHANG' option. A good place to put a
such a check for terminated and stopped jobs is just before prompting
for a new command.
The shell can also receive asynchronous notification that there is
status information available for a child process by establishing a
handler for `SIGCHLD' signals. *Note Signal Handling::.
In the sample shell program, the `SIGCHLD' signal is normally
ignored. This is to avoid reentrancy problems involving the global data
structures the shell manipulates. But at specific times when the shell
is not using these data structures--such as when it is waiting for
input on the terminal--it makes sense to enable a handler for
`SIGCHLD'. The same function that is used to do the synchronous status
checks (`do_job_notification', in this case) can also be called from
within this handler.
Here are the parts of the sample shell program that deal with
checking the status of jobs and reporting the information to the user.
/* Store the status of the process PID that was returned by waitpid.
Return 0 if all went well, nonzero otherwise. */
mark_process_status (pid_t pid, int status)
job *j;
process *p;
if (pid > 0)
/* Update the record for the process. */
for (j = first_job; j; j = j->next)
for (p = j->first_process; p; p = p->next)
if (p->pid == pid)
p->status = status;
if (WIFSTOPPED (status))
p->stopped = 1;
p->completed = 1;
if (WIFSIGNALED (status))
fprintf (stderr, "%d: Terminated by signal %d.\n",
(int) pid, WTERMSIG (p->status));
return 0;
fprintf (stderr, "No child process %d.\n", pid);
return -1;
else if (pid == 0 || errno == ECHILD)
/* No processes ready to report. */
return -1;
else {
/* Other weird errors. */
perror ("waitpid");
return -1;
/* Check for processes that have status information available,
without blocking. */
update_status (void)
int status;
pid_t pid;
pid = waitpid (WAIT_ANY, &status, WUNTRACED|WNOHANG);
while (!mark_process_status (pid, status));
/* Check for processes that have status information available,
blocking until all processes in the given job have reported. */
wait_for_job (job *j)
int status;
pid_t pid;
pid = waitpid (WAIT_ANY, &status, WUNTRACED);
while (!mark_process_status (pid, status)
&& !job_is_stopped (j)
&& !job_is_completed (j));
/* Format information about job status for the user to look at. */
format_job_info (job *j, const char *status)
fprintf (stderr, "%ld (%s): %s\n", (long)j->pgid, status, j->command);
/* Notify the user about stopped or terminated jobs.
Delete terminated jobs from the active job list. */
do_job_notification (void)
job *j, *jlast, *jnext;
process *p;
/* Update status information for child processes. */
update_status ();
jlast = NULL;
for (j = first_job; j; j = jnext)
jnext = j->next;
/* If all processes have completed, tell the user the job has
completed and delete it from the list of active jobs. */
if (job_is_completed (j)) {
format_job_info (j, "completed");
if (jlast)
jlast->next = jnext;
first_job = jnext;
free_job (j);
/* Notify the user about stopped jobs,
marking them so that we won't do this more than once. */
else if (job_is_stopped (j) && !j->notified) {
format_job_info (j, "stopped");
j->notified = 1;
jlast = j;
/* Don't say anything about jobs that are still running. */
jlast = j;

File:, Node: Continuing Stopped Jobs, Next: Missing Pieces, Prev: Stopped and Terminated Jobs, Up: Implementing a Shell
27.6.6 Continuing Stopped Jobs
The shell can continue a stopped job by sending a `SIGCONT' signal to
its process group. If the job is being continued in the foreground,
the shell should first invoke `tcsetpgrp' to give the job access to the
terminal, and restore the saved terminal settings. After continuing a
job in the foreground, the shell should wait for the job to stop or
complete, as if the job had just been launched in the foreground.
The sample shell program handles both newly created and continued
jobs with the same pair of functions, `put_job_in_foreground' and
`put_job_in_background'. The definitions of these functions were given
in *note Foreground and Background::. When continuing a stopped job, a
nonzero value is passed as the CONT argument to ensure that the
`SIGCONT' signal is sent and the terminal modes reset, as appropriate.
This leaves only a function for updating the shell's internal
bookkeeping about the job being continued:
/* Mark a stopped job J as being running again. */
mark_job_as_running (job *j)
Process *p;
for (p = j->first_process; p; p = p->next)
p->stopped = 0;
j->notified = 0;
/* Continue the job J. */
continue_job (job *j, int foreground)
mark_job_as_running (j);
if (foreground)
put_job_in_foreground (j, 1);
put_job_in_background (j, 1);

File:, Node: Missing Pieces, Prev: Continuing Stopped Jobs, Up: Implementing a Shell
27.6.7 The Missing Pieces
The code extracts for the sample shell included in this chapter are only
a part of the entire shell program. In particular, nothing at all has
been said about how `job' and `program' data structures are allocated
and initialized.
Most real shells provide a complex user interface that has support
for a command language; variables; abbreviations, substitutions, and
pattern matching on file names; and the like. All of this is far too
complicated to explain here! Instead, we have concentrated on showing
how to implement the core process creation and job control functions
that can be called from such a shell.
Here is a table summarizing the major entry points we have presented:
`void init_shell (void)'
Initialize the shell's internal state. *Note Initializing the
`void launch_job (job *J, int FOREGROUND)'
Launch the job J as either a foreground or background job. *Note
Launching Jobs::.
`void do_job_notification (void)'
Check for and report any jobs that have terminated or stopped.
Can be called synchronously or within a handler for `SIGCHLD'
signals. *Note Stopped and Terminated Jobs::.
`void continue_job (job *J, int FOREGROUND)'
Continue the job J. *Note Continuing Stopped Jobs::.
Of course, a real shell would also want to provide other functions
for managing jobs. For example, it would be useful to have commands to
list all active jobs or to send a signal (such as `SIGKILL') to a job.

File:, Node: Functions for Job Control, Prev: Implementing a Shell, Up: Job Control
27.7 Functions for Job Control
This section contains detailed descriptions of the functions relating
to job control.
* Menu:
* Identifying the Terminal:: Determining the controlling terminal's name.
* Process Group Functions:: Functions for manipulating process groups.
* Terminal Access Functions:: Functions for controlling terminal access.

File:, Node: Identifying the Terminal, Next: Process Group Functions, Up: Functions for Job Control
27.7.1 Identifying the Controlling Terminal
You can use the `ctermid' function to get a file name that you can use
to open the controlling terminal. In the GNU C Library, it returns the
same string all the time: `"/dev/tty"'. That is a special "magic" file
name that refers to the controlling terminal of the current process (if
it has one). To find the name of the specific terminal device, use
`ttyname'; *note Is It a Terminal::.
The function `ctermid' is declared in the header file `stdio.h'.
-- Function: char * ctermid (char *STRING)
The `ctermid' function returns a string containing the file name of
the controlling terminal for the current process. If STRING is
not a null pointer, it should be an array that can hold at least
`L_ctermid' characters; the string is returned in this array.
Otherwise, a pointer to a string in a static area is returned,
which might get overwritten on subsequent calls to this function.
An empty string is returned if the file name cannot be determined
for any reason. Even if a file name is returned, access to the
file it represents is not guaranteed.
-- Macro: int L_ctermid
The value of this macro is an integer constant expression that
represents the size of a string large enough to hold the file name
returned by `ctermid'.
See also the `isatty' and `ttyname' functions, in *note Is It a

File:, Node: Process Group Functions, Next: Terminal Access Functions, Prev: Identifying the Terminal, Up: Functions for Job Control
27.7.2 Process Group Functions
Here are descriptions of the functions for manipulating process groups.
Your program should include the header files `sys/types.h' and
`unistd.h' to use these functions.
-- Function: pid_t setsid (void)
The `setsid' function creates a new session. The calling process
becomes the session leader, and is put in a new process group whose
process group ID is the same as the process ID of that process.
There are initially no other processes in the new process group,
and no other process groups in the new session.
This function also makes the calling process have no controlling
The `setsid' function returns the new process group ID of the
calling process if successful. A return value of `-1' indicates an
error. The following `errno' error conditions are defined for this
The calling process is already a process group leader, or
there is already another process group around that has the
same process group ID.
-- Function: pid_t getsid (pid_t PID)
The `getsid' function returns the process group ID of the session
leader of the specified process. If a PID is `0', the process
group ID of the session leader of the current process is returned.
In case of error `-1' is returned and `errno' is set. The
following `errno' error conditions are defined for this function:
There is no process with the given process ID PID.
The calling process and the process specified by PID are in
different sessions, and the implementation doesn't allow to
access the process group ID of the session leader of the
process with ID PID from the calling process.
The `getpgrp' function has two definitions: one derived from BSD
Unix, and one from the POSIX.1 standard. The feature test macros you
have selected (*note Feature Test Macros::) determine which definition
you get. Specifically, you get the BSD version if you define
`_BSD_SOURCE'; otherwise, you get the POSIX version if you define
`_POSIX_SOURCE' or `_GNU_SOURCE'. Programs written for old BSD systems
will not include `unistd.h', which defines `getpgrp' specially under
`_BSD_SOURCE'. You must link such programs with the `-lbsd-compat'
option to get the BSD definition.
-- POSIX.1 Function: pid_t getpgrp (void)
The POSIX.1 definition of `getpgrp' returns the process group ID of
the calling process.
-- BSD Function: pid_t getpgrp (pid_t PID)
The BSD definition of `getpgrp' returns the process group ID of the
process PID. You can supply a value of `0' for the PID argument
to get information about the calling process.
-- System V Function: int getpgid (pid_t PID)
`getpgid' is the same as the BSD function `getpgrp'. It returns
the process group ID of the process PID. You can supply a value
of `0' for the PID argument to get information about the calling
In case of error `-1' is returned and `errno' is set. The
following `errno' error conditions are defined for this function:
There is no process with the given process ID PID. The
calling process and the process specified by PID are in
different sessions, and the implementation doesn't allow to
access the process group ID of the process with ID PID from
the calling process.
-- Function: int setpgid (pid_t PID, pid_t PGID)
The `setpgid' function puts the process PID into the process group
PGID. As a special case, either PID or PGID can be zero to
indicate the process ID of the calling process.
This function fails on a system that does not support job control.
*Note Job Control is Optional::, for more information.
If the operation is successful, `setpgid' returns zero. Otherwise
it returns `-1'. The following `errno' error conditions are
defined for this function:
The child process named by PID has executed an `exec'
function since it was forked.
The value of the PGID is not valid.
The system doesn't support job control.
The process indicated by the PID argument is a session leader,
or is not in the same session as the calling process, or the
value of the PGID argument doesn't match a process group ID
in the same session as the calling process.
The process indicated by the PID argument is not the calling
process or a child of the calling process.
-- Function: int setpgrp (pid_t PID, pid_t PGID)
This is the BSD Unix name for `setpgid'. Both functions do exactly
the same thing.

File:, Node: Terminal Access Functions, Prev: Process Group Functions, Up: Functions for Job Control
27.7.3 Functions for Controlling Terminal Access
These are the functions for reading or setting the foreground process
group of a terminal. You should include the header files `sys/types.h'
and `unistd.h' in your application to use these functions.
Although these functions take a file descriptor argument to specify
the terminal device, the foreground job is associated with the terminal
file itself and not a particular open file descriptor.
-- Function: pid_t tcgetpgrp (int FILEDES)
This function returns the process group ID of the foreground
process group associated with the terminal open on descriptor
If there is no foreground process group, the return value is a
number greater than `1' that does not match the process group ID
of any existing process group. This can happen if all of the
processes in the job that was formerly the foreground job have
terminated, and no other job has yet been moved into the
In case of an error, a value of `-1' is returned. The following
`errno' error conditions are defined for this function:
The FILEDES argument is not a valid file descriptor.
The system doesn't support job control.
The terminal file associated with the FILEDES argument isn't
the controlling terminal of the calling process.
-- Function: int tcsetpgrp (int FILEDES, pid_t PGID)
This function is used to set a terminal's foreground process group
ID. The argument FILEDES is a descriptor which specifies the
terminal; PGID specifies the process group. The calling process
must be a member of the same session as PGID and must have the same
controlling terminal.
For terminal access purposes, this function is treated as output.
If it is called from a background process on its controlling
terminal, normally all processes in the process group are sent a
`SIGTTOU' signal. The exception is if the calling process itself
is ignoring or blocking `SIGTTOU' signals, in which case the
operation is performed and no signal is sent.
If successful, `tcsetpgrp' returns `0'. A return value of `-1'
indicates an error. The following `errno' error conditions are
defined for this function:
The FILEDES argument is not a valid file descriptor.
The PGID argument is not valid.
The system doesn't support job control.
The FILEDES isn't the controlling terminal of the calling
The PGID isn't a process group in the same session as the
calling process.
-- Function: pid_t tcgetsid (int FILDES)
This function is used to obtain the process group ID of the session
for which the terminal specified by FILDES is the controlling
terminal. If the call is successful the group ID is returned.
Otherwise the return value is `(pid_t) -1' and the global variable
ERRNO is set to the following value:
The FILEDES argument is not a valid file descriptor.
The calling process does not have a controlling terminal, or
the file is not the controlling terminal.

File:, Node: Name Service Switch, Next: Users and Groups, Prev: Job Control, Up: Top
28 System Databases and Name Service Switch
Various functions in the C Library need to be configured to work
correctly in the local environment. Traditionally, this was done by
using files (e.g., `/etc/passwd'), but other nameservices (like the
Network Information Service (NIS) and the Domain Name Service (DNS))
became popular, and were hacked into the C library, usually with a fixed
search order.
The GNU C Library contains a cleaner solution of this problem. It is
designed after a method used by Sun Microsystems in the C library of
Solaris 2. The GNU C Library follows their name and calls this scheme
"Name Service Switch" (NSS).
Though the interface might be similar to Sun's version there is no
common code. We never saw any source code of Sun's implementation and
so the internal interface is incompatible. This also manifests in the
file names we use as we will see later.
* Menu:
* NSS Basics:: What is this NSS good for.
* NSS Configuration File:: Configuring NSS.
* NSS Module Internals:: How does it work internally.
* Extending NSS:: What to do to add services or databases.

File:, Node: NSS Basics, Next: NSS Configuration File, Prev: Name Service Switch, Up: Name Service Switch
28.1 NSS Basics
The basic idea is to put the implementation of the different services
offered to access the databases in separate modules. This has some
1. Contributors can add new services without adding them to the GNU C
2. The modules can be updated separately.
3. The C library image is smaller.
To fulfill the first goal above the ABI of the modules will be
described below. For getting the implementation of a new service right
it is important to understand how the functions in the modules get
called. They are in no way designed to be used by the programmer
directly. Instead the programmer should only use the documented and
standardized functions to access the databases.
The databases available in the NSS are
Mail aliases
Ethernet numbers,
Groups of users, *note Group Database::.
Host names and numbers, *note Host Names::.
Network wide list of host and users, *note Netgroup Database::.
Network names and numbers, *note Networks Database::.
Network protocols, *note Protocols Database::.
User passwords, *note User Database::.
Remote procedure call names and numbers,
Network services, *note Services Database::.
Shadow user passwords,
There will be some more added later (`automount', `bootparams',
`netmasks', and `publickey').

File:, Node: NSS Configuration File, Next: NSS Module Internals, Prev: NSS Basics, Up: Name Service Switch
28.2 The NSS Configuration File
Somehow the NSS code must be told about the wishes of the user. For
this reason there is the file `/etc/nsswitch.conf'. For each database
this file contain a specification how the lookup process should work.
The file could look like this:
# /etc/nsswitch.conf
# Name Service Switch configuration file.
passwd: db files nis
shadow: files
group: db files nis
hosts: files nisplus nis dns
networks: nisplus [NOTFOUND=return] files
ethers: nisplus [NOTFOUND=return] db files
protocols: nisplus [NOTFOUND=return] db files
rpc: nisplus [NOTFOUND=return] db files
services: nisplus [NOTFOUND=return] db files
The first column is the database as you can guess from the table
above. The rest of the line specifies how the lookup process works.
Please note that you specify the way it works for each database
individually. This cannot be done with the old way of a monolithic
The configuration specification for each database can contain two