load(n) Tcl (7.5) load(n)
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NAME
load - Load machine code and initialize new commands.
SYNOPSIS
load fileName
load fileName packageName
load fileName packageName interp
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DESCRIPTION
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. fileName 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 .so file
under Solaris or a DLL under Windows. packageName is the
name of the package, and is used to compute the name of an
initialization procedure. interp is the path name of the
interpreter into which to load the package (see the interp
manual entry for details); if interp is omitted, it defaults
to the interpreter in which the load command was invoked.
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 packageName and
whether or not the target interpreter is a safe one. For
normal interpreters the name of the initialization procedure
will have the form pkg_Init, where pkg is the same as
packageName except that the first letter is converted to
upper case and all other letters are converted to lower
case. For example, if packageName is foo or FOo, the
initialization procedure's name will be Foo_Init.
If the target interpreter is a safe interpreter, then the
name of the initialization procedure will be pkg_SafeInit
instead of pkg_Init. The pkg_SafeInit 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 safe manual entry.
The initialization procedure must match the following
prototype:
typedef int Tcl_PackageInitProc(Tcl_Interp *interp);
The interp argument identifies the interpreter in which the
package is to be loaded. The initialization procedure must
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load(n) Tcl (7.5) load(n)
return TCL_OK or TCL_ERROR to indicate whether or not it
completed successfully; in the event of an error it should
set interp->result to point to an error message. The result
of the load command will be the result returned by the
initialization procedure.
The actual loading of a file will only be done once for each
fileName in an application. If a given fileName is loaded
into multiple interpreters, then the first load will load
the code and call the initialization procedure; subsequent
loads will call the initialization procedure without loading
the code again. It is not possible to unload or reload a
package.
The load command also supports packages that are statically
linked with the application, if those packages have been
registered by calling the Tcl_StaticPackage procedure. If
fileName is an empty string, then packageName must be
specified.
If packageName 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 fileName, strip off the first three characters if
they are lib, and use any following alphabetic and underline |
characters as the module name. For example, the command
load libxyz4.2.so uses the module name xyz and the command
load bin/last.so {} uses the module name last.
If fileName is an empty string, then packageName must be |
specified. The load command first searches for a statically |
loaded package (one that has been registered by calling the |
Tcl_StaticPackage procedure) by that name; if one is found, |
it is used. Otherwise, the load command searches for a |
dynamically loaded package by that name, and uses it if it |
is found. If several different files have been loaded with |
different versions of the package, Tcl picks the file that |
was loaded first.
BUGS
If the same file is loaded by different fileNames, 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).
SEE ALSO
info sharedlibextension, Tcl_StaticPackage, safe(n)
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load(n) Tcl (7.5) load(n)
KEYWORDS
binary code, loading, safe interpreter, shared library
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