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From: RayeR <glaux AT centrum DOT cz>
Newsgroups: comp.os.msdos.djgpp
Subject: Re: argv[0]
Date: Sun, 4 Dec 2011 14:22:28 -0800 (PST)
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To: djgpp AT delorie DOT com
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Reply-To: djgpp AT delorie DOT com

Aha, I didn't imagine that it may go wrong when use tools like redir.
I personally didn't face the problem yet but it may be an issue.
Georg, I fully understand what do you need because I need it for the
same purpose. Here's my code I use of portable function but it rely on
argv[0] so now I know it's not 100% perfect :(

/
****************************************************************************/
/*                   How to get program execution
directory                 */
/
****************************************************************************/
/* Created: 21.2.2011 [DJGPP/MINGW32/
LINUX]                                 */
/* Last modified: 21.2.2011 [DJGPP/MINGW32/
LINUX]                           */
/* Copyright (C) 2011 by
RayeR                                          */
/
****************************************************************************/
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#if defined __WIN32__
#include <windows.h>
#elif defined __linux__
#endif

int getexecdir(char *argv0, char *obuffer, int osize)
{
  char *last_backslash_in_path;
#ifdef __WIN32__
  GetModuleFileName(NULL, obuffer, osize); // get exec path
  obuffer[osize-1]=0;                  // trim to buffer size
#elif defined __linux__
  char path[1024];                     // auxiliary path
  struct stat stat_buf;
  strncpy(path, "/proc/self/exe", 1023); // exec path is in this file
  while (1)
    {
    size_t size=readlink(path, obuffer, osize-1);
    if (size==(size_t)~0)
      {
      obuffer[0]=0;
      break;
      }
    else
      {
      if (size>=osize)
        obuffer[osize-1]=0;
      else
        obuffer[size]=0;
      int i=stat(obuffer, &stat_buf);
      if (i==-1)
        break;
      else if (!S_ISLNK(stat_buf.st_mode))
        break;
      strncpy(obuffer, path, osize-1);
      obuffer[osize-1]=0;
      }
    }
#else
  strncpy(obuffer, argv0, osize);
  obuffer[osize-1]=0;
#endif
  last_backslash_in_path=strrchr(obuffer, '\\'); // find the last
backlash in the exec path
  if (last_backslash_in_path==NULL)    // if none
    last_backslash_in_path=strrchr(obuffer, '/'); // try to find
normal slash in the exec path
  if (last_backslash_in_path==NULL)
    {
    strcpy(obuffer, "./");             // use current directory
    return(-1);
    }
  else                                 // else copy exec path up to
last backslash (included)
    last_backslash_in_path[1]=0;       // cut off exec name from path
  return(0);
}

int main(int argc, char *argv[])
{
  char path[1024];
  getexecdir(argv[0], path, 1024);
  printf("execdir = %s\n", path);
  return(0);
}