load(7,n)(n) Tcl Built-In Commands load(7,n)(n) NAME load(7,n) - Load machine code and initialize new commands. SYNOPSIS load(7,n) fileName load(7,n) fileName packageName load(7,n) fileName packageName interp DESCRIPTION This command loads binary code from a file(1,n) into the application's address space and calls an initialization procedure in(1,8) the package to incorporate it into an interpreter. fileName is the name of the file(1,n) 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(1,n) under Solaris or a DLL under Windows. packageName is the name of the pack- age, and is used to compute the name of an initialization procedure. interp is the path name of the interpreter into which to load(7,n) the pack- age (see the interp manual entry for details); if(3,n) interp is omitted, it defaults to the interpreter in(1,8) which the load(7,n) command was invoked. Once the file(1,n) has been loaded into the application's address space, one of two initialization procedures will be invoked in(1,8) the new code. Typ- ically 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(3,n) 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 initial- izes the safe interpreter only with partial functionality provided by the package that is safe for use by untrusted code. For more informa- tion on Safe-Tcl, see the safe manual entry. The initialization procedure must match the following prototype: type- def int Tcl_PackageInitProc(Tcl_Interp *interp); The interp argument identifies the interpreter in(1,8) 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(1,8) the event of an error(8,n) it should set(7,n,1 builtins) the interpreter's result to point to an error(8,n) message. The result of the load(7,n) command will be the result returned by the initial- ization procedure. The actual loading of a file(1,n) will only be done once for each fileName in(1,8) an application. If a given fileName is loaded into multiple inter- preters, then the first load(7,n) will load(7,n) the code and call the initial- ization procedure; subsequent load(7,n)s will call the initialization pro- cedure without loading the code again. It is not possible to unload or reload a package. The load(7,n) command also supports packages that are statically linked with the application, if(3,n) those packages have been registered by calling the Tcl_StaticPackage procedure. If fileName is an empty string(3,n), then packageName must be specified. If packageName is omitted or specified as an empty string(3,n), Tcl tries to guess the name of the package. This may be done differently on differ- ent platforms. The default guess, which is used on most UNIX plat- forms, is to take the last element of fileName, strip off the first three characters if(3,n) they are lib, and use any following alphabetic and underline characters as the module name. For example, the command load(7,n) libxyz4.2.so uses the module name xyz and the command load(7,n) bin/last.so {} uses the module name last. If fileName is an empty string(3,n), then packageName must be specified. The load(7,n) command first searches for a statically loaded package (one that has been registered by calling the Tcl_StaticPackage procedure) by that name; if(3,n) one is found, it is used. Otherwise, the load(7,n) command searches for a dynamically loaded package by that name, and uses it if(3,n) it is found. If several different files have been load(7,n)ed with differ- ent versions of the package, Tcl picks the file(1,n) that was loaded first. PORTABILITY ISSUES Windows When a load(7,n) fails with "library not found" error(8,n), it is also possible that a dependent library was not found. To see the dependent libraries, type ``dumpbin -imports <dllname>'' in(1,8) a DOS console(4,n) to see what the library must import. When loading a DLL in(1,8) the current directory, Windows will ignore ``./'' as a path specifier and use a search heuristic to find the DLL instead. To avoid this, load(7,n) the DLL with load(7,n) [file(1,n) join(1,n) [pwd(1,n,1 builtins)] mylib.DLL] BUGS If the same file(1,n) is load(7,n)ed 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(1,5,n) sharedlibextension, Tcl_StaticPackage(3), safe(n) KEYWORDS binary code, loading, safe interpreter, shared library Tcl 7.5 load(7,n)(n)