glibc/posix/execvp.c

/* Copyright (C) 1991, 1992, 1995, 1996 Free Software Foundation, Inc.
This file is part of the GNU C Library.

The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Library General Public License as
published by the Free Software Foundation; either version 2 of the
License, or (at your option) any later version.

The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
Library General Public License for more details.

You should have received a copy of the GNU Library General Public
License along with the GNU C Library; see the file COPYING.LIB.  If
not, write to the Free Software Foundation, Inc., 675 Mass Ave,
Cambridge, MA 02139, USA.  */

#include <unistd.h>
#include <stdarg.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <paths.h>

/* Execute FILE, searching in the `PATH' environment variable if it contains
   no slashes, with arguments ARGV and environment from `environ'.  */
int
execvp (file, argv)
     const char *file;
     char *const argv[];
{
  void execute (const char *file, char *const argv[])
    {
      execv (file, argv);

      if (errno == ENOEXEC)
	{
	  /* The file is accessible but it is not an executable file.
	     Invoke the shell to interpret it as a script.  */

	  int argc;
	  char **new_argv;

	  /* Count the arguments.  */
	  for (argc = 0; argv[argc++];);

	  /* Construct an argument list for the shell.  */
	  new_argv = __alloca ((argc + 1) * sizeof (char *));
	  for (new_argv[0] = _PATH_BSHELL; argc > 0; --argc)
	    new_argv[argc] = argv[argc - 1];

	  /* Execute the shell.  */
	  execv (new_argv[0], new_argv);
	}
    }

  if (strchr (file, '/') != NULL)
    /* Don't search when it contains a slash.  */
    execute (file, argv);
  else
    {
      char *path, *p, *name;
      size_t len;

      path = getenv ("PATH");
      if (path == NULL)
	{
	  /* There is no `PATH' in the environment.
	     The default search path is the current directory
	     followed by the path `confstr' returns for `_CS_PATH'.  */
	  len = confstr (_CS_PATH, (char *) NULL, 0);
	  path = (char *) __alloca (1 + len);
	  path[0] = ':';
	  (void) confstr (_CS_PATH, path + 1, len);
	}

      len = strlen (file) + 1;
      name = __alloca (strlen (path) + len);
      p = path;
      do
	{
	  path = p;
	  p = strchr (path, ':');
	  if (p == NULL)
	    p = strchr (path, '\0');

	  if (p == path)
	    /* Two adjacent colons, or a colon at the beginning or the end
	       of `PATH' means to search the current directory.  */
	    (void) memcpy (name, file, len);
	  else
	    {
	      /* Construct the pathname to try.  */
	      (void) memcpy (name, path, p - path);
	      name[p - path] = '/';
	      (void) memcpy (&name[(p - path) + 1], file, len);
	    }

	  /* Try to execute this name.  If it works, execv will not return.  */
	  execute (name, argv);

	  switch (errno)
	    {
	    case ENOENT:
	    case EACCES:
	      /* Those errors indicate the file is missing or not executable
		 by us, in which case we want to just try the next path
		 directory.  */
	      break;

	    default:
	      /* Some other error means we found an executable file, but
		 something went wrong executing it; return the error to our
		 caller.  */
	      return -1;
	    }
	}
      while (*p++ != '\0');
    }

  /* We tried every element and none of them worked.
     Return the error from the last attempt (probably ENOENT).  */
  return -1;
}