osx man page for tcl_getnameofexecutable

Tcl_FindExecutable(3)					      Tcl Library Procedures					     Tcl_FindExecutable(3)

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

SYNOPSIS
       #include <tcl.h>

       void
       Tcl_FindExecutable(argv0)

       const char *
       Tcl_GetNameOfExecutable()

ARGUMENTS
       char *argv0 (in) 	 The first command-line argument to the program, which gives the application's name.
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DESCRIPTION
       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 info nameofexecutable command.

       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 info
       nameofexecutable will return an empty string.

       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 info nameofexecutable command.  NULL is returned if the internal full path name has not
       been computed or unknown.

KEYWORDS
       binary, executable file

Tcl									8.1						     Tcl_FindExecutable(3)