man/mann/load.n

'\"
'\" Copyright (c) 1995-1996 Sun Microsystems, Inc.
'\"
'\" See the file "license.terms" for information on usage and redistribution
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
'\" 
'\" RCS: @(#) $Id: load.n,v 1.7 2002/07/01 18:24:39 jenglish Exp $
'\" 
'\" The definitions below are for supplemental macros used in Tcl/Tk
'\" manual entries.
'\"
'\" .AP type name in/out ?indent?
'\"	Start paragraph describing an argument to a library procedure.
'\"	type is type of argument (int, etc.), in/out is either "in", "out",
'\"	or "in/out" to describe whether procedure reads or modifies arg,
'\"	and indent is equivalent to second arg of .IP (shouldn't ever be
'\"	needed;  use .AS below instead)
'\"
'\" .AS ?type? ?name?
'\"	Give maximum sizes of arguments for setting tab stops.  Type and
'\"	name are examples of largest possible arguments that will be passed
'\"	to .AP later.  If args are omitted, default tab stops are used.
'\"
'\" .BS
'\"	Start box enclosure.  From here until next .BE, everything will be
'\"	enclosed in one large box.
'\"
'\" .BE
'\"	End of box enclosure.
'\"
'\" .CS
'\"	Begin code excerpt.
'\"
'\" .CE
'\"	End code excerpt.
'\"
'\" .VS ?version? ?br?
'\"	Begin vertical sidebar, for use in marking newly-changed parts
'\"	of man pages.  The first argument is ignored and used for recording
'\"	the version when the .VS was added, so that the sidebars can be
'\"	found and removed when they reach a certain age.  If another argument
'\"	is present, then a line break is forced before starting the sidebar.
'\"
'\" .VE
'\"	End of vertical sidebar.
'\"
'\" .DS
'\"	Begin an indented unfilled display.
'\"
'\" .DE
'\"	End of indented unfilled display.
'\"
'\" .SO
'\"	Start of list of standard options for a Tk widget.  The
'\"	options follow on successive lines, in four columns separated
'\"	by tabs.
'\"
'\" .SE
'\"	End of list of standard options for a Tk widget.
'\"
'\" .OP cmdName dbName dbClass
'\"	Start of description of a specific option.  cmdName gives the
'\"	option's name as specified in the class command, dbName gives
'\"	the option's name in the option database, and dbClass gives
'\"	the option's class in the option database.
'\"
'\" .UL arg1 arg2
'\"	Print arg1 underlined, then print arg2 normally.
'\"
'\" RCS: @(#) $Id: man.macros,v 1.4 2000/08/25 06:18:32 ericm Exp $
'\"
'\"	# Set up traps and other miscellaneous stuff for Tcl/Tk man pages.
.if t .wh -1.3i ^B
.nr ^l \n(.l
.ad b
'\"	# Start an argument description
.de AP
.ie !"\\$4"" .TP \\$4
.el \{\
.   ie !"\\$2"" .TP \\n()Cu
.   el          .TP 15
.\}
.ta \\n()Au \\n()Bu
.ie !"\\$3"" \{\
\&\\$1	\\fI\\$2\\fP	(\\$3)
.\".b
.\}
.el \{\
.br
.ie !"\\$2"" \{\
\&\\$1	\\fI\\$2\\fP
.\}
.el \{\
\&\\fI\\$1\\fP
.\}
.\}
..
'\"	# define tabbing values for .AP
.de AS
.nr )A 10n
.if !"\\$1"" .nr )A \\w'\\$1'u+3n
.nr )B \\n()Au+15n
.\"
.if !"\\$2"" .nr )B \\w'\\$2'u+\\n()Au+3n
.nr )C \\n()Bu+\\w'(in/out)'u+2n
..
.AS Tcl_Interp Tcl_CreateInterp in/out
'\"	# BS - start boxed text
'\"	# ^y = starting y location
'\"	# ^b = 1
.de BS
.br
.mk ^y
.nr ^b 1u
.if n .nf
.if n .ti 0
.if n \l'\\n(.lu\(ul'
.if n .fi
..
'\"	# BE - end boxed text (draw box now)
.de BE
.nf
.ti 0
.mk ^t
.ie n \l'\\n(^lu\(ul'
.el \{\
.\"	Draw four-sided box normally, but don't draw top of
.\"	box if the box started on an earlier page.
.ie !\\n(^b-1 \{\
\h'-1.5n'\L'|\\n(^yu-1v'\l'\\n(^lu+3n\(ul'\L'\\n(^tu+1v-\\n(^yu'\l'|0u-1.5n\(ul'
.\}
.el \}\
\h'-1.5n'\L'|\\n(^yu-1v'\h'\\n(^lu+3n'\L'\\n(^tu+1v-\\n(^yu'\l'|0u-1.5n\(ul'
.\}
.\}
.fi
.br
.nr ^b 0
..
'\"	# VS - start vertical sidebar
'\"	# ^Y = starting y location
'\"	# ^v = 1 (for troff;  for nroff this doesn't matter)
.de VS
.if !"\\$2"" .br
.mk ^Y
.ie n 'mc \s12\(br\s0
.el .nr ^v 1u
..
'\"	# VE - end of vertical sidebar
.de VE
.ie n 'mc
.el \{\
.ev 2
.nf
.ti 0
.mk ^t
\h'|\\n(^lu+3n'\L'|\\n(^Yu-1v\(bv'\v'\\n(^tu+1v-\\n(^Yu'\h'-|\\n(^lu+3n'
.sp -1
.fi
.ev
.\}
.nr ^v 0
..
'\"	# Special macro to handle page bottom:  finish off current
'\"	# box/sidebar if in box/sidebar mode, then invoked standard
'\"	# page bottom macro.
.de ^B
.ev 2
'ti 0
'nf
.mk ^t
.if \\n(^b \{\
.\"	Draw three-sided box if this is the box's first page,
.\"	draw two sides but no top otherwise.
.ie !\\n(^b-1 \h'-1.5n'\L'|\\n(^yu-1v'\l'\\n(^lu+3n\(ul'\L'\\n(^tu+1v-\\n(^yu'\h'|0u'\c
.el \h'-1.5n'\L'|\\n(^yu-1v'\h'\\n(^lu+3n'\L'\\n(^tu+1v-\\n(^yu'\h'|0u'\c
.\}
.if \\n(^v \{\
.nr ^x \\n(^tu+1v-\\n(^Yu
\kx\h'-\\nxu'\h'|\\n(^lu+3n'\ky\L'-\\n(^xu'\v'\\n(^xu'\h'|0u'\c
.\}
.bp
'fi
.ev
.if \\n(^b \{\
.mk ^y
.nr ^b 2
.\}
.if \\n(^v \{\
.mk ^Y
.\}
..
'\"	# DS - begin display
.de DS
.RS
.nf
.sp
..
'\"	# DE - end display
.de DE
.fi
.RE
.sp
..
'\"	# SO - start of list of standard options
.de SO
.SH "STANDARD OPTIONS"
.LP
.nf
.ta 5.5c 11c
.ft B
..
'\"	# SE - end of list of standard options
.de SE
.fi
.ft R
.LP
See the \\fBoptions\\fR manual entry for details on the standard options.
..
'\"	# OP - start of full description for a single option
.de OP
.LP
.nf
.ta 4c
Command-Line Name:	\\fB\\$1\\fR
Database Name:	\\fB\\$2\\fR
Database Class:	\\fB\\$3\\fR
.fi
.IP
..
'\"	# CS - begin code excerpt
.de CS
.RS
.nf
.ta .25i .5i .75i 1i
..
'\"	# CE - end code excerpt
.de CE
.fi
.RE
..
.de UL
\\$1\l'|0\(ul'\\$2
..
.TH load n 7.5 Tcl "Tcl Built-In Commands"
.BS
'\" Note:  do not modify the .SH NAME line immediately below!
.SH NAME
load \- Load machine code and initialize new commands.
.SH SYNOPSIS
\fBload \fIfileName\fR
.br
\fBload \fIfileName packageName\fR
.br
\fBload \fIfileName packageName interp\fR
.BE

.SH DESCRIPTION
.PP
This command loads binary code from a file into the
application's address space and calls an initialization procedure
in the package to incorporate it into an interpreter.  \fIfileName\fR
is the name of the file containing the code;  its exact form varies
from system to system but on most systems it is a shared library,
such as a \fB.so\fR file under Solaris or a DLL under Windows.
\fIpackageName\fR is the name of the package, and is used to
compute the name of an initialization procedure.
\fIinterp\fR is the path name of the interpreter into which to load
the package (see the \fBinterp\fR manual entry for details);
if \fIinterp\fR is omitted, it defaults to the
interpreter in which the \fBload\fR command was invoked.
.PP
Once the file has been loaded into the application's address space,
one of two initialization procedures will be invoked in the new code.
Typically the initialization procedure will add new commands to a
Tcl interpreter.
The name of the initialization procedure is determined by
\fIpackageName\fR and whether or not the target interpreter
is a safe one.  For normal interpreters the name of the initialization
procedure will have the form \fIpkg\fB_Init\fR, where \fIpkg\fR
is the same as \fIpackageName\fR except that the first letter is
converted to upper case and all other letters
are converted to lower case.  For example, if \fIpackageName\fR is
\fBfoo\fR or \fBFOo\fR, the initialization procedure's name will
be \fBFoo_Init\fR.
.PP
If the target interpreter is a safe interpreter, then the name
of the initialization procedure will be \fIpkg\fB_SafeInit\fR
instead of \fIpkg\fB_Init\fR.
The \fIpkg\fB_SafeInit\fR function should be written carefully, so that it
initializes the safe interpreter only with partial functionality provided
by the package that is safe for use by untrusted code. For more information
on Safe\-Tcl, see the \fBsafe\fR manual entry.
.PP
The initialization procedure must match the following prototype:
.CS
typedef int Tcl_PackageInitProc(Tcl_Interp *\fIinterp\fR);
.CE
The \fIinterp\fR argument identifies the interpreter in which the
package is to be loaded.  The initialization procedure must return
\fBTCL_OK\fR or \fBTCL_ERROR\fR to indicate whether or not it completed
successfully;  in the event of an error it should set the interpreter's result
to point to an error message.  The result of the \fBload\fR command
will be the result returned by the initialization procedure.
.PP
The actual loading of a file will only be done once for each \fIfileName\fR
in an application.  If a given \fIfileName\fR is loaded into multiple
interpreters, then the first \fBload\fR will load the code and
call the initialization procedure;  subsequent \fBload\fRs will
call the initialization procedure without loading the code again.
It is not possible to unload or reload a package.
.PP
The \fBload\fR command also supports packages that are statically
linked with the application, if those packages have been registered
by calling the \fBTcl_StaticPackage\fR procedure.
If \fIfileName\fR is an empty string, then \fIpackageName\fR must
be specified.
.PP
If \fIpackageName\fR is omitted or specified as an empty string,
Tcl tries to guess the name of the package.
This may be done differently on different platforms.
The default guess, which is used on most UNIX platforms, is to
take the last element of \fIfileName\fR, strip off the first
three characters if they are \fBlib\fR, and use any following
.VS
alphabetic and underline characters as the module name.
.VE
For example, the command \fBload libxyz4.2.so\fR uses the module
name \fBxyz\fR and the command \fBload bin/last.so {}\fR uses the
module name \fBlast\fR.
.VS "" br
.PP
If \fIfileName\fR is an empty string, then \fIpackageName\fR must
be specified.
The \fBload\fR command first searches for a statically loaded package
(one that has been registered by calling the \fBTcl_StaticPackage\fR
procedure) by that name; if one is found, it is used.
Otherwise, the \fBload\fR command searches for a dynamically loaded
package by that name, and uses it if it is found.  If several
different files have been \fBload\fRed with different versions of
the package, Tcl picks the file that was loaded first.
.VE

.SH "PORTABILITY ISSUES"
.TP
\fBWindows\fR\0\0\0\0\0
.
When a load fails with "library not found" error, it is also possible
that a dependent library was not found.  To see the dependent libraries,
type ``dumpbin -imports <dllname>'' in a DOS console to see what the
library must import.
When loading a DLL in the current directory, Windows will ignore ``./'' as
a path specifier and use a search heuristic to find the DLL instead.
To avoid this, load the DLL with
.CS
    load [file join [pwd] mylib.DLL]
.CE

.SH BUGS
.PP
If the same file is \fBload\fRed by different \fIfileName\fRs, it will
be loaded into the process's address space multiple times.  The
behavior of this varies from system to system (some systems may
detect the redundant loads, others may not).

.SH "SEE ALSO"
info sharedlibextension, Tcl_StaticPackage(3), safe(n)

.SH KEYWORDS
binary code, loading, safe interpreter, shared library