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.so man.macros

.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 \fIinterp->result\fR

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 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"

\fBinfo sharedlibextension\fR, Tcl_StaticPackage, safe(n)

.SH KEYWORDS

binary code, loading, safe interpreter, shared library