glibc/posix/execvp.c

/* Copyright (C) 1991, 92, 95, 96, 97, 98 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., 59 Temple Place - Suite 330,
   Boston, MA 02111-1307, USA.  */

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


static void
internal_function
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.  */

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

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

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


/* 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[];
{
  int got_eacces = 0;

  if (*file == '\0')
    {
      /* We check the simple case first. */
      __set_errno (ENOENT);
      return -1;
    }

  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.  */
	      char *tmp = __mempcpy (name, path, p - path);
	      *tmp++ = '/';
	      (void) __mempcpy (tmp, file, len);
	    }

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

	  switch (errno)
	    {
	    case EACCES:
	      /* Record the we got a `Permission denied' error.  If we end
		 up finding no executable we can use, we want to diagnose
		 that we did find one but were denied access.  */
	      got_eacces = 1;
	    case ENOENT:
	    case ESTALE:
	    case ENOTDIR:
	      /* 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.  */

  if (got_eacces)
    /* At least one failure was due to permissions, so report that error.  */
    __set_errno (EACCES);

  /* Return the error from the last attempt (probably ENOENT).  */
  return -1;
}