Страницы справочника OS X

Эта страница руководства для  версии 10.9 Mac OS X

Читать страницы руководства

load(n)                                     Tcl Built-In Commands                                    load(n)



____________________________________________________________________________________________________________

NAME
       load - Load machine code and initialize new commands

SYNOPSIS
       load fileName
       load fileName packageName
       load fileName packageName interp
____________________________________________________________________________________________________________


DESCRIPTION
       This command loads binary code from a file into the application's address space and calls an initial-ization initialization
       ization 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 proce-dures procedures
       dures 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 initialization
       tialization  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 initializa-tion initialization
       tion  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 the interpreter's 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.  For Tcl versions lower than 8.5, it is not possible to unload or reload  a  package. |
       From  version 8.5 however, the unload command allows the unloading of libraries loaded with load, for |
       libraries that are aware of the Tcl's unloading mechanism.

       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  pack-age. package.
       age.   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 proce-dure) procedure)
       dure)  by that name; if one is found, it is used.  Otherwise, the load command searches for a dynami-cally dynamically
       cally 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.

PORTABILITY ISSUES
       Windows
              When a load fails with "library not found" error, it is also possible that a dependent library
              was not found.  To see the dependent libraries, type "dumpbin -imports  <dllname>"  in  a  DOS
              console  to  see  what  the library must import.  When loading a DLL in the current directory,
              Windows will ignore "./" as a path specifier and use  a  search  heuristic  to  find  the  DLL
              instead.  To avoid this, load the DLL with:
              load [file join [pwd] mylib.DLL]

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).

EXAMPLE
       The following is a minimal extension:

              #include <tcl.h>
              #include <stdio.h>
              static int fooCmd(ClientData clientData,
                      Tcl_Interp *interp, int objc, Tcl_Obj *const objv[]) {
                  printf("called with %d arguments\n", objc);
                  return TCL_OK;
              }
              int Foo_Init(Tcl_Interp *interp) {
                  if (Tcl_InitStubs(interp, "8.1", 0) == NULL) {
                return TCL_ERROR;
                  }
                  printf("creating foo command");
                  Tcl_CreateObjCommand(interp, "foo", fooCmd, NULL, NULL);
                  return TCL_OK;
              }

       When  built into a shared/dynamic library with a suitable name (e.g. foo.dll on Windows, libfoo.so on
       Solaris and Linux) it can then be loaded into Tcl with the following:

              # Load the extension
              switch $tcl_platform(platform) {
                 windows {
                    load [file join [pwd] foo.dll]
                 }
                 unix {
                    load [file join [pwd] libfoo[info sharedlibextension]]
                 }
              }

              # Now execute the command defined by the extension
              foo


SEE ALSO
       info sharedlibextension, Tcl_StaticPackage(3), safe(n)


KEYWORDS
       binary code, loading, safe interpreter, shared library



Tcl                                                  7.5                                             load(n)