Tcl_FindExecutable, Tcl_GetNameOfExecutable - identify or return the name of the binary file containing

       char *argv0 (in)          The first command-line argument to the program, which gives  the  application's
                                 name.
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       The  Tcl_FindExecutable  procedure  computes  the  full  path  name of the executable file from which the
       application was invoked and saves it for Tcl's internal use.  The executable's path name  is  needed  for
       several  purposes  in Tcl.  For example, it is needed on some platforms in the implementation of the load
       command.  It is also returned by the infonameofexecutable command.

       The  result  of  Tcl_FindExecutable  is  the   full   Tcl   version   with   build   information   (e.g.,
       9.0.0+abcdef...abcdef.gcc-1002).

       On  UNIX  platforms this procedure is typically invoked as the very first thing in the application's main
       program;  it must be passed argv[0] as its argument.  It is important not to change the working directory
       before the invocation.  Tcl_FindExecutable uses argv0 along with the PATH environment  variable  to  find
       the  application's  executable,  if  possible.  If it fails to find the binary, then future calls to infonameofexecutable will return an empty string.

       On Windows platforms this procedure is typically invoked as the very first  thing  in  the  application's
       main  program  as well; Its argv[0] argument is only used to indicate whether the executable has a stderr
       channel (any non-null value) or not (the value null). If Tcl_SetPanicProc is never called and no debugger
       is running, this determines whether the panic message is sent to stderr or to a standard system dialog.

       Tcl_GetNameOfExecutable simply returns a pointer to the internal full path name of the executable file as
       computed by Tcl_FindExecutable.  This procedure call is the C API equivalent to the infonameofexecutable
       command.  NULL is returned if the internal full path name has not been computed or unknown.

       Tcl_FindExecutable can not be used in stub-enabled extensions.

       binary, executable file

Tcl                                                    8.1                              Tcl_FindExecutable(3tcl)

       Tcl_FindExecutable,  Tcl_GetNameOfExecutable  - identify or return the name of the binary file containing
       the application

#include<tcl.h>

       const char *
       Tcl_FindExecutable(argv0)

       const char *
       Tcl_GetNameOfExecutable()