load(n) Tcl Built-In Commands load(n)_________________________________________________________________NAMEload - Load machine code and initialize new commands.
SYNOPSISload fileName
load fileName packageName
load fileName packageName interp
_________________________________________________________________DESCRIPTION
This command loads binary code from a file into the appli-
cation's address space and calls an initialization proce-
dure 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 sys-
tems 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 ini-
tialization 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 ini-
tialization procedure will have the form pkg_Init, where
pkg is the same as packageName except that the first let-
ter 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 initialization procedure must match the following pro-
totype:
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 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
Tcl 7.5 1
load(n) Tcl Built-In Commands load(n)
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 stati-
cally linked with the application, if those packages have
been registered by calling the Tcl_StaticPackage proce-
dure. 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 alpha- |
betic 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 mod-
ule name last.
If fileName is an empty string, then packageName must be |
specified. The load command first searches for a stati- |
cally 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
KEYWORDS
binary code, loading, shared library
Tcl 7.5 2
