source: git/Singular/find_exec.c @ 445016

/****************************************
*  Computer Algebra System SINGULAR     *
****************************************/
/* $id:$ */

/* find_exec.c -- Find a program, given an argv[0]
   Copyright (C) 1996 Free Software Foundation, Inc.
   Copyright (C) 1990 by W. Wilson Ho.
   This file is part of the GNU Dld Library. */

/* Adapted for use with Singular by obachman@mathematik.uni-kl.de  4/98*/

#include "mod2.h"

#if ! defined(MSDOS) && ! defined(__MWERKS__) && \
    defined(HAVE_SYS_TYPES_H) && defined(HAVE_PWD_H)&&defined(HAVE_SYS_PARAM_H)

#include <sys/types.h>
#include <unistd.h> /* always defiend */
#include <pwd.h>

#include <stdlib.h>
#include <sys/stat.h>

#ifdef HAVE_SYS_FILE_H
# include <sys/file.h> /* can live without it */
#endif
#include <sys/param.h>
#include <strings.h>

#include "mmemory.h"

#ifndef MAXPATHLEN
#define MAXPATHLEN 1024
#endif


/* Do not return copies of sth, but simply the strings
   -- we make copies later */
#define copy_of(string) mstrdup(string)

/* ABSOLUTE_FILENAME_P (fname): True if fname is an absolute filename */
#ifdef atarist
#define ABSOLUTE_FILENAME_P(fname)        ((fname[0] == '/') || \
        (fname[0] && (fname[1] == ':')))
#else
#define ABSOLUTE_FILENAME_P(fname)        (fname[0] == '/')
#endif /* atarist */

/* Return the absolute name of the program named NAME.  This function
   searches the directories in the PATH environment variable if PROG
   has no directory components. */
#ifndef HAVE_READLINK
char * find_executable (const char *name)
#else
char * find_executable_link (const char *name)
#endif
{
  char *search;
  char *p;
  char *extra = NULL;
  char tbuf[MAXPATHLEN];

  if (ABSOLUTE_FILENAME_P(name)) {
      /* If we can execute the named file then return it. */
      if (! access (name, X_OK)) 
        return copy_of (name);
    }
  else {
    if (((name[0] == '.') && (name[1] == '/')) || 
        ((name[0] == '.') && (name[1] == '.') && (name[2] == '/'))) {

      strcpy (tbuf, (name[1] == '.' ? ".." : "."));
      
#ifdef HAVE_GETCWD
      getcwd (tbuf, MAXPATHLEN);
#else
# ifdef HAVE_GETWD
      getwd (tbuf);
# endif
#endif
      strcat (tbuf, "/");
      strcat (tbuf, name);
      return copy_of (tbuf);
    }


    search = getenv("PATH");
/* for winnt under msdos, cwd is implicetyly in the path */
#ifdef WINNT
    p = getenv("SHELL");
    if (p == NULL || strlen(p < 2))
    {
      /* we are under msdos display */
      extra = (char*) AllocL((search != NULL ? strlen(search) : 0) + 3);
      sprintf(extra, ".:");
      if (search != NULL) strcat(extra, search);
      search = extra;
    }
#endif
    p = search;

    while (*p) {
      char *next;
      next = tbuf;

      /* Perform tilde-expansion. Stolen from GNU readline/tilde.c. */
      if (p[0] == '~') {
        if (! p[1] || p[1] == '/') {
          /* Prepend $HOME to the rest of the string. */
          char *temp_home = (char *) getenv ("HOME");

          /* If there is no HOME variable, look up the directory in the
             password database. */
          if (! temp_home) {
            struct passwd *entry;

            entry = getpwuid (getuid ());
            if (entry)
              temp_home = entry->pw_dir;
          }

          strcpy (tbuf, temp_home);
          next = tbuf + strlen (tbuf);
          p ++;
        }
        else {
          char username[MAXPATHLEN];
          struct passwd *user_entry;
          int i;

          p ++;                        /* Skip the tilde. */
          for (i = 0; *p && *p != '/' && *p != ':'; i++)
            username[i] = *p ++;
          username[i] = '\0';

          user_entry = getpwnam (username);
          if (user_entry) {
            strcpy (tbuf, user_entry->pw_dir);
            next = tbuf + strlen (tbuf);
          }
        }

        endpwent ();
      }

      /* Copy directory name into [tbuf]. */
      while (*p && *p != ':')
        *next ++ = *p ++;
      *next = '\0';
      if (*p != '\0')
        p ++;

      if (tbuf[0] == '.' && tbuf[1] == '\0') {
#ifdef HAVE_GETCWD
        getcwd (tbuf, MAXPATHLEN);
#else
# ifdef HAVE_GETWD
        getwd (tbuf);
# endif
#endif
      }

      strcat (tbuf, "/");
      strcat (tbuf, name);

      /* If we can execute the named file, then return it. */
      if (! access (tbuf, X_OK)) {
#ifdef WINNT
        if (extra != NULL)
          FreeL(extra);
#endif
        return copy_of (tbuf);
      }
    }
  }

  return NULL;
}

#ifdef HAVE_READLINK
char * find_executable (const char *name)
{
  char * link = find_executable_link(name);
  char buf[MAXPATHLEN];
  int ret;

  if (link == NULL && (ret=readlink(name, buf, MAXPATHLEN)) > 0)
  {
    buf[ret] ='\0';
    link = find_executable_link(buf);
  }
  // follow, if we have a link
  if (link != NULL && (ret=readlink(link, buf, MAXPATHLEN)) > 0)
  {
    char *p = strrchr(link, '/');
    char *executable;

    
    if(p!=NULL) *(p+1)='\0';
    buf[ret]='\0';
    
    if (buf[0] != '/')
    {
      executable = (char*) AllocL(strlen(link) + ret + 1);
      strcpy(executable, link);
      strcat(executable, buf);
    }
    else
    {
      executable = copy_of(buf);
    }
    
    FreeL(link);
    return executable;
  }

  return link;
}
#endif /* HAVE_READLINK */

#else

char* find_executable (const char *name)
{
  return NULL;
}

#endif /* #if ! defined(MSDOS) && ! defined(__MWERKS__) && defined(HAVE_SYS_TYPES_H) && defined(HAVE_PWD_H)&&defined(HAVE_SYS_PARAM_H) */