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 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.
"" br
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.
