grub-core/commands/test.c - chromiumos/third_party/grub2 - Git at Google

 /* test.c -- The test command..  */
 /*
  *  GRUB  --  GRand Unified Bootloader
  *  Copyright (C) 2005,2007,2009  Free Software Foundation, Inc.
  *
  *  GRUB is free software: you can redistribute it and/or modify
  *  it under the terms of the GNU General Public License as published by
  *  the Free Software Foundation, either version 3 of the License, or
  *  (at your option) any later version.
  *
  *  GRUB 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 General Public License for more details.
  *
  *  You should have received a copy of the GNU General Public License
  *  along with GRUB.  If not, see <http://www.gnu.org/licenses/>.
  */

 #include <grub/dl.h>
 #include <grub/misc.h>
 #include <grub/mm.h>
 #include <grub/env.h>
 #include <grub/fs.h>
 #include <grub/device.h>
 #include <grub/file.h>
 #include <grub/command.h>
 #include <grub/i18n.h>

 GRUB_MOD_LICENSE ("GPLv3+");

 /* A simple implementation for signed numbers. */
 static int
 grub_strtosl (char *arg, char **end, int base)
 {
   if (arg[0] == '-')
     return -grub_strtoul (arg + 1, end, base);
   return grub_strtoul (arg, end, base);
 }

 /* Parse a test expression starting from *argn. */
 static int
 test_parse (char **args, int *argn, int argc)
 {
   int ret = 0, discard = 0, invert = 0;
   int file_exists;
   struct grub_dirhook_info file_info;

   auto void update_val (int val);
   auto void get_fileinfo (char *pathname);

   /* Take care of discarding and inverting. */
   void update_val (int val)
   {
     if (! discard)
       ret = invert ? ! val : val;
     invert = discard = 0;
   }

   /* Check if file exists and fetch its information. */
   void get_fileinfo (char *path)
   {
     char *filename, *pathname;
     char *device_name;
     grub_fs_t fs;
     grub_device_t dev;

     /* A hook for iterating directories. */
     auto int find_file (const char *cur_filename,
 			const struct grub_dirhook_info *info);
     int find_file (const char *cur_filename,
 		   const struct grub_dirhook_info *info)
     {
       if ((info->case_insensitive ? grub_strcasecmp (cur_filename, filename)
 	   : grub_strcmp (cur_filename, filename)) == 0)
 	{
 	  file_info = *info;
 	  file_exists = 1;
 	  return 1;
 	}
       return 0;
     }

     file_exists = 0;
     device_name = grub_file_get_device_name (path);
     dev = grub_device_open (device_name);
     if (! dev)
       {
 	grub_free (device_name);
 	return;
       }

     fs = grub_fs_probe (dev);
     if (! fs)
       {
 	grub_free (device_name);
 	grub_device_close (dev);
 	return;
       }

     pathname = grub_strchr (path, ')');
     if (! pathname)
       pathname = path;
     else
       pathname++;

     /* Remove trailing '/'. */
     while (*pathname && pathname[grub_strlen (pathname) - 1] == '/')
       pathname[grub_strlen (pathname) - 1] = 0;

     /* Split into path and filename. */
     filename = grub_strrchr (pathname, '/');
     if (! filename)
       {
 	path = grub_strdup ("/");
 	filename = pathname;
       }
     else
       {
 	filename++;
 	path = grub_strdup (pathname);
 	path[filename - pathname] = 0;
       }

     /* It's the whole device. */
     if (! *pathname)
       {
 	file_exists = 1;
 	grub_memset (&file_info, 0, sizeof (file_info));
 	/* Root is always a directory. */
 	file_info.dir = 1;

 	/* Fetch writing time. */
 	file_info.mtimeset = 0;
 	if (fs->mtime)
 	  {
 	    if (! fs->mtime (dev, &file_info.mtime))
 	      file_info.mtimeset = 1;
 	    grub_errno = GRUB_ERR_NONE;
 	  }
       }
     else
       (fs->dir) (dev, path, find_file);

     grub_device_close (dev);
     grub_free (path);
     grub_free (device_name);
   }

   /* Here we have the real parsing. */
   while (*argn < argc)
     {
       /* First try 3 argument tests. */
       if (*argn + 2 < argc)
 	{
 	  /* String tests. */
 	  if (grub_strcmp (args[*argn + 1], "=") == 0
 	      || grub_strcmp (args[*argn + 1], "==") == 0)
 	    {
 	      update_val (grub_strcmp (args[*argn], args[*argn + 2]) == 0);
 	      (*argn) += 3;
 	      continue;
 	    }

 	  if (grub_strcmp (args[*argn + 1], "!=") == 0)
 	    {
 	      update_val (grub_strcmp (args[*argn], args[*argn + 2]) != 0);
 	      (*argn) += 3;
 	      continue;
 	    }

 	  /* GRUB extension: lexicographical sorting. */
 	  if (grub_strcmp (args[*argn + 1], "<") == 0)
 	    {
 	      update_val (grub_strcmp (args[*argn], args[*argn + 2]) < 0);
 	      (*argn) += 3;
 	      continue;
 	    }

 	  if (grub_strcmp (args[*argn + 1], "<=") == 0)
 	    {
 	      update_val (grub_strcmp (args[*argn], args[*argn + 2]) <= 0);
 	      (*argn) += 3;
 	      continue;
 	    }

 	  if (grub_strcmp (args[*argn + 1], ">") == 0)
 	    {
 	      update_val (grub_strcmp (args[*argn], args[*argn + 2]) > 0);
 	      (*argn) += 3;
 	      continue;
 	    }

 	  if (grub_strcmp (args[*argn + 1], ">=") == 0)
 	    {
 	      update_val (grub_strcmp (args[*argn], args[*argn + 2]) >= 0);
 	      (*argn) += 3;
 	      continue;
 	    }

 	  /* Number tests. */
 	  if (grub_strcmp (args[*argn + 1], "-eq") == 0)
 	    {
 	      update_val (grub_strtosl (args[*argn], 0, 0)
 			  == grub_strtosl (args[*argn + 2], 0, 0));
 	      (*argn) += 3;
 	      continue;
 	    }

 	  if (grub_strcmp (args[*argn + 1], "-ge") == 0)
 	    {
 	      update_val (grub_strtosl (args[*argn], 0, 0)
 			  >= grub_strtosl (args[*argn + 2], 0, 0));
 	      (*argn) += 3;
 	      continue;
 	    }

 	  if (grub_strcmp (args[*argn + 1], "-gt") == 0)
 	    {
 	      update_val (grub_strtosl (args[*argn], 0, 0)
 			  > grub_strtosl (args[*argn + 2], 0, 0));
 	      (*argn) += 3;
 	      continue;
 	    }

 	  if (grub_strcmp (args[*argn + 1], "-le") == 0)
 	    {
 	      update_val (grub_strtosl (args[*argn], 0, 0)
 		      <= grub_strtosl (args[*argn + 2], 0, 0));
 	      (*argn) += 3;
 	      continue;
 	    }

 	  if (grub_strcmp (args[*argn + 1], "-lt") == 0)
 	    {
 	      update_val (grub_strtosl (args[*argn], 0, 0)
 			  < grub_strtosl (args[*argn + 2], 0, 0));
 	      (*argn) += 3;
 	      continue;
 	    }

 	  if (grub_strcmp (args[*argn + 1], "-ne") == 0)
 	    {
 	      update_val (grub_strtosl (args[*argn], 0, 0)
 			  != grub_strtosl (args[*argn + 2], 0, 0));
 	      (*argn) += 3;
 	      continue;
 	    }

 	  /* GRUB extension: compare numbers skipping prefixes.
 	     Useful for comparing versions. E.g. vmlinuz-2 -plt vmlinuz-11. */
 	  if (grub_strcmp (args[*argn + 1], "-pgt") == 0
 	      || grub_strcmp (args[*argn + 1], "-plt") == 0)
 	    {
 	      int i;
 	      /* Skip common prefix. */
 	      for (i = 0; args[*argn][i] == args[*argn + 2][i]
 		     && args[*argn][i]; i++);

 	      /* Go the digits back. */
 	      i--;
 	      while (grub_isdigit (args[*argn][i]) && i > 0)
 		i--;
 	      i++;

 	      if (grub_strcmp (args[*argn + 1], "-pgt") == 0)
 		update_val (grub_strtoul (args[*argn] + i, 0, 0)
 			    > grub_strtoul (args[*argn + 2] + i, 0, 0));
 	      else
 		update_val (grub_strtoul (args[*argn] + i, 0, 0)
 			    < grub_strtoul (args[*argn + 2] + i, 0, 0));
 	      (*argn) += 3;
 	      continue;
 	    }

 	  /* -nt and -ot tests. GRUB extension: when doing -?t<bias> bias
 	     will be added to the first mtime. */
 	  if (grub_memcmp (args[*argn + 1], "-nt", 3) == 0
 	      || grub_memcmp (args[*argn + 1], "-ot", 3) == 0)
 	    {
 	      struct grub_dirhook_info file1;
 	      int file1exists;
 	      int bias = 0;

 	      /* Fetch fileinfo. */
 	      get_fileinfo (args[*argn]);
 	      file1 = file_info;
 	      file1exists = file_exists;
 	      get_fileinfo (args[*argn + 2]);

 	      if (args[*argn + 1][3])
 		bias = grub_strtosl (args[*argn + 1] + 3, 0, 0);

 	      if (grub_memcmp (args[*argn + 1], "-nt", 3) == 0)
 		update_val ((file1exists && ! file_exists)
 			    || (file1.mtimeset && file_info.mtimeset
 				&& file1.mtime + bias > file_info.mtime));
 	      else
 		update_val ((! file1exists && file_exists)
 			    || (file1.mtimeset && file_info.mtimeset
 				&& file1.mtime + bias < file_info.mtime));
 	      (*argn) += 3;
 	      continue;
 	    }
 	}

       /* Two-argument tests. */
       if (*argn + 1 < argc)
 	{
 	  /* File tests. */
 	  if (grub_strcmp (args[*argn], "-d") == 0)
 	    {
 	      get_fileinfo (args[*argn + 1]);
 	      update_val (file_exists && file_info.dir);
 	      (*argn) += 2;
 	      return ret;
 	    }

 	  if (grub_strcmp (args[*argn], "-e") == 0)
 	    {
 	      get_fileinfo (args[*argn + 1]);
 	      update_val (file_exists);
 	      (*argn) += 2;
 	      return ret;
 	    }

 	  if (grub_strcmp (args[*argn], "-f") == 0)
 	    {
 	      get_fileinfo (args[*argn + 1]);
 	      /* FIXME: check for other types. */
 	      update_val (file_exists && ! file_info.dir);
 	      (*argn) += 2;
 	      return ret;
 	    }

 	  if (grub_strcmp (args[*argn], "-s") == 0)
 	    {
 	      grub_file_t file;
 	      grub_file_filter_disable_compression ();
 	      file = grub_file_open (args[*argn + 1]);
 	      update_val (file && (grub_file_size (file) != 0));
 	      if (file)
 		grub_file_close (file);
 	      grub_errno = GRUB_ERR_NONE;
 	      (*argn) += 2;
 	      return ret;
 	    }

 	  /* String tests. */
 	  if (grub_strcmp (args[*argn], "-n") == 0)
 	    {
 	      update_val (args[*argn + 1][0]);

 	      (*argn) += 2;
 	      continue;
 	    }
 	  if (grub_strcmp (args[*argn], "-z") == 0)
 	    {
 	      update_val (! args[*argn + 1][0]);
 	      (*argn) += 2;
 	      continue;
 	    }
 	}

       /* Special modifiers. */

       /* End of expression. return to parent. */
       if (grub_strcmp (args[*argn], ")") == 0)
 	{
 	  (*argn)++;
 	  return ret;
 	}
       /* Recursively invoke if parenthesis. */
       if (grub_strcmp (args[*argn], "(") == 0)
 	{
 	  (*argn)++;
 	  update_val (test_parse (args, argn, argc));
 	  continue;
 	}

       if (grub_strcmp (args[*argn], "!") == 0)
 	{
 	  invert = ! invert;
 	  (*argn)++;
 	  continue;
 	}
       if (grub_strcmp (args[*argn], "-a") == 0)
 	{
 	  /* If current value is 0 second value is to be discarded. */
 	  discard = ! ret;
 	  (*argn)++;
 	  continue;
 	}
       if (grub_strcmp (args[*argn], "-o") == 0)
 	{
 	  /* If current value is 1 second value is to be discarded. */
 	  discard = ret;
 	  (*argn)++;
 	  continue;
 	}

       /* No test found. Interpret if as just a string. */
       update_val (args[*argn][0]);
       (*argn)++;
     }
   return ret;
 }

 static grub_err_t
 grub_cmd_test (grub_command_t cmd __attribute__ ((unused)),
 	       int argc, char **args)
 {
   int argn = 0;

   if (argc >= 1 && grub_strcmp (args[argc - 1], "]") == 0)
     argc--;

   return test_parse (args, &argn, argc) ? GRUB_ERR_NONE
     : grub_error (GRUB_ERR_TEST_FAILURE, N_("false"));
 }

 static grub_command_t cmd_1, cmd_2;

 GRUB_MOD_INIT(test)
 {
   cmd_1 = grub_register_command ("[", grub_cmd_test,
 				 N_("EXPRESSION ]"), N_("Evaluate an expression."));
   cmd_1->flags |= GRUB_COMMAND_FLAG_EXTRACTOR;
   cmd_2 = grub_register_command ("test", grub_cmd_test,
 				 N_("EXPRESSION"), N_("Evaluate an expression."));
   cmd_2->flags |= GRUB_COMMAND_FLAG_EXTRACTOR;
 }

 GRUB_MOD_FINI(test)
 {
   grub_unregister_command (cmd_1);
   grub_unregister_command (cmd_2);
 }
	/* test.c -- The test command.. */
	/*
	* GRUB -- GRand Unified Bootloader
	* Copyright (C) 2005,2007,2009 Free Software Foundation, Inc.
	*
	* GRUB is free software: you can redistribute it and/or modify
	* it under the terms of the GNU General Public License as published by
	* the Free Software Foundation, either version 3 of the License, or
	* (at your option) any later version.
	*
	* GRUB 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 General Public License for more details.
	*
	* You should have received a copy of the GNU General Public License
	* along with GRUB. If not, see <http://www.gnu.org/licenses/>.
	*/

	#include <grub/dl.h>
	#include <grub/misc.h>
	#include <grub/mm.h>
	#include <grub/env.h>
	#include <grub/fs.h>
	#include <grub/device.h>
	#include <grub/file.h>
	#include <grub/command.h>
	#include <grub/i18n.h>

	GRUB_MOD_LICENSE ("GPLv3+");

	/* A simple implementation for signed numbers. */
	static int
	grub_strtosl (char arg, char *end, int base)
	{
	if (arg[0] == '-')
	return -grub_strtoul (arg + 1, end, base);
	return grub_strtoul (arg, end, base);
	}

	/* Parse a test expression starting from argn. /
	static int
	test_parse (char *args, int argn, int argc)
	{
	int ret = 0, discard = 0, invert = 0;
	int file_exists;
	struct grub_dirhook_info file_info;

	auto void update_val (int val);
	auto void get_fileinfo (char *pathname);

	/* Take care of discarding and inverting. */
	void update_val (int val)
	{
	if (! discard)
	ret = invert ? ! val : val;
	invert = discard = 0;
	}

	/* Check if file exists and fetch its information. */
	void get_fileinfo (char *path)
	{
	char filename, pathname;
	char *device_name;
	grub_fs_t fs;
	grub_device_t dev;

	/* A hook for iterating directories. */
	auto int find_file (const char *cur_filename,
	const struct grub_dirhook_info *info);
	int find_file (const char *cur_filename,
	const struct grub_dirhook_info *info)
	{
	if ((info->case_insensitive ? grub_strcasecmp (cur_filename, filename)
	: grub_strcmp (cur_filename, filename)) == 0)
	{
	file_info = *info;
	file_exists = 1;
	return 1;
	}
	return 0;
	}

	file_exists = 0;
	device_name = grub_file_get_device_name (path);
	dev = grub_device_open (device_name);
	if (! dev)
	{
	grub_free (device_name);
	return;
	}

	fs = grub_fs_probe (dev);
	if (! fs)
	{
	grub_free (device_name);
	grub_device_close (dev);
	return;
	}

	pathname = grub_strchr (path, ')');
	if (! pathname)
	pathname = path;
	else
	pathname++;

	/* Remove trailing '/'. */
	while (*pathname && pathname[grub_strlen (pathname) - 1] == '/')
	pathname[grub_strlen (pathname) - 1] = 0;

	/* Split into path and filename. */
	filename = grub_strrchr (pathname, '/');
	if (! filename)
	{
	path = grub_strdup ("/");
	filename = pathname;
	}
	else
	{
	filename++;
	path = grub_strdup (pathname);
	path[filename - pathname] = 0;
	}

	/* It's the whole device. */
	if (! *pathname)
	{
	file_exists = 1;
	grub_memset (&file_info, 0, sizeof (file_info));
	/* Root is always a directory. */
	file_info.dir = 1;

	/* Fetch writing time. */
	file_info.mtimeset = 0;
	if (fs->mtime)
	{
	if (! fs->mtime (dev, &file_info.mtime))
	file_info.mtimeset = 1;
	grub_errno = GRUB_ERR_NONE;
	}
	}
	else
	(fs->dir) (dev, path, find_file);

	grub_device_close (dev);
	grub_free (path);
	grub_free (device_name);
	}

	/* Here we have the real parsing. */
	while (*argn < argc)
	{
	/* First try 3 argument tests. */
	if (*argn + 2 < argc)
	{
	/* String tests. */
	if (grub_strcmp (args[*argn + 1], "=") == 0
	\|\| grub_strcmp (args[*argn + 1], "==") == 0)
	{
	update_val (grub_strcmp (args[argn], args[argn + 2]) == 0);
	(*argn) += 3;
	continue;
	}

	if (grub_strcmp (args[*argn + 1], "!=") == 0)
	{
	update_val (grub_strcmp (args[argn], args[argn + 2]) != 0);
	(*argn) += 3;
	continue;
	}

	/* GRUB extension: lexicographical sorting. */
	if (grub_strcmp (args[*argn + 1], "<") == 0)
	{
	update_val (grub_strcmp (args[argn], args[argn + 2]) < 0);
	(*argn) += 3;
	continue;
	}

	if (grub_strcmp (args[*argn + 1], "<=") == 0)
	{
	update_val (grub_strcmp (args[argn], args[argn + 2]) <= 0);
	(*argn) += 3;
	continue;
	}

	if (grub_strcmp (args[*argn + 1], ">") == 0)
	{
	update_val (grub_strcmp (args[argn], args[argn + 2]) > 0);
	(*argn) += 3;
	continue;
	}

	if (grub_strcmp (args[*argn + 1], ">=") == 0)
	{
	update_val (grub_strcmp (args[argn], args[argn + 2]) >= 0);
	(*argn) += 3;
	continue;
	}

	/* Number tests. */
	if (grub_strcmp (args[*argn + 1], "-eq") == 0)
	{
	update_val (grub_strtosl (args[*argn], 0, 0)
	== grub_strtosl (args[*argn + 2], 0, 0));
	(*argn) += 3;
	continue;
	}

	if (grub_strcmp (args[*argn + 1], "-ge") == 0)
	{
	update_val (grub_strtosl (args[*argn], 0, 0)
	>= grub_strtosl (args[*argn + 2], 0, 0));
	(*argn) += 3;
	continue;
	}

	if (grub_strcmp (args[*argn + 1], "-gt") == 0)
	{
	update_val (grub_strtosl (args[*argn], 0, 0)
	> grub_strtosl (args[*argn + 2], 0, 0));
	(*argn) += 3;
	continue;
	}

	if (grub_strcmp (args[*argn + 1], "-le") == 0)
	{
	update_val (grub_strtosl (args[*argn], 0, 0)
	<= grub_strtosl (args[*argn + 2], 0, 0));
	(*argn) += 3;
	continue;
	}

	if (grub_strcmp (args[*argn + 1], "-lt") == 0)
	{
	update_val (grub_strtosl (args[*argn], 0, 0)
	< grub_strtosl (args[*argn + 2], 0, 0));
	(*argn) += 3;
	continue;
	}

	if (grub_strcmp (args[*argn + 1], "-ne") == 0)
	{
	update_val (grub_strtosl (args[*argn], 0, 0)
	!= grub_strtosl (args[*argn + 2], 0, 0));
	(*argn) += 3;
	continue;
	}

	/* GRUB extension: compare numbers skipping prefixes.
	Useful for comparing versions. E.g. vmlinuz-2 -plt vmlinuz-11. */
	if (grub_strcmp (args[*argn + 1], "-pgt") == 0
	\|\| grub_strcmp (args[*argn + 1], "-plt") == 0)
	{
	int i;
	/* Skip common prefix. */
	for (i = 0; args[argn][i] == args[argn + 2][i]
	&& args[*argn][i]; i++);

	/* Go the digits back. */
	i--;
	while (grub_isdigit (args[*argn][i]) && i > 0)
	i--;
	i++;

	if (grub_strcmp (args[*argn + 1], "-pgt") == 0)
	update_val (grub_strtoul (args[*argn] + i, 0, 0)
	> grub_strtoul (args[*argn + 2] + i, 0, 0));
	else
	update_val (grub_strtoul (args[*argn] + i, 0, 0)
	< grub_strtoul (args[*argn + 2] + i, 0, 0));
	(*argn) += 3;
	continue;
	}

	/* -nt and -ot tests. GRUB extension: when doing -?t<bias> bias
	will be added to the first mtime. */
	if (grub_memcmp (args[*argn + 1], "-nt", 3) == 0
	\|\| grub_memcmp (args[*argn + 1], "-ot", 3) == 0)
	{
	struct grub_dirhook_info file1;
	int file1exists;
	int bias = 0;

	/* Fetch fileinfo. */
	get_fileinfo (args[*argn]);
	file1 = file_info;
	file1exists = file_exists;
	get_fileinfo (args[*argn + 2]);

	if (args[*argn + 1][3])
	bias = grub_strtosl (args[*argn + 1] + 3, 0, 0);

	if (grub_memcmp (args[*argn + 1], "-nt", 3) == 0)
	update_val ((file1exists && ! file_exists)
	\|\| (file1.mtimeset && file_info.mtimeset
	&& file1.mtime + bias > file_info.mtime));
	else
	update_val ((! file1exists && file_exists)
	\|\| (file1.mtimeset && file_info.mtimeset
	&& file1.mtime + bias < file_info.mtime));
	(*argn) += 3;
	continue;
	}
	}

	/* Two-argument tests. */
	if (*argn + 1 < argc)
	{
	/* File tests. */
	if (grub_strcmp (args[*argn], "-d") == 0)
	{
	get_fileinfo (args[*argn + 1]);
	update_val (file_exists && file_info.dir);
	(*argn) += 2;
	return ret;
	}

	if (grub_strcmp (args[*argn], "-e") == 0)
	{
	get_fileinfo (args[*argn + 1]);
	update_val (file_exists);
	(*argn) += 2;
	return ret;
	}

	if (grub_strcmp (args[*argn], "-f") == 0)
	{
	get_fileinfo (args[*argn + 1]);
	/* FIXME: check for other types. */
	update_val (file_exists && ! file_info.dir);
	(*argn) += 2;
	return ret;
	}

	if (grub_strcmp (args[*argn], "-s") == 0)
	{
	grub_file_t file;
	grub_file_filter_disable_compression ();
	file = grub_file_open (args[*argn + 1]);
	update_val (file && (grub_file_size (file) != 0));
	if (file)
	grub_file_close (file);
	grub_errno = GRUB_ERR_NONE;
	(*argn) += 2;
	return ret;
	}

	/* String tests. */
	if (grub_strcmp (args[*argn], "-n") == 0)
	{
	update_val (args[*argn + 1][0]);

	(*argn) += 2;
	continue;
	}
	if (grub_strcmp (args[*argn], "-z") == 0)
	{
	update_val (! args[*argn + 1][0]);
	(*argn) += 2;
	continue;
	}
	}

	/* Special modifiers. */

	/* End of expression. return to parent. */
	if (grub_strcmp (args[*argn], ")") == 0)
	{
	(*argn)++;
	return ret;
	}
	/* Recursively invoke if parenthesis. */
	if (grub_strcmp (args[*argn], "(") == 0)
	{
	(*argn)++;
	update_val (test_parse (args, argn, argc));
	continue;
	}

	if (grub_strcmp (args[*argn], "!") == 0)
	{
	invert = ! invert;
	(*argn)++;
	continue;
	}
	if (grub_strcmp (args[*argn], "-a") == 0)
	{
	/* If current value is 0 second value is to be discarded. */
	discard = ! ret;
	(*argn)++;
	continue;
	}
	if (grub_strcmp (args[*argn], "-o") == 0)
	{
	/* If current value is 1 second value is to be discarded. */
	discard = ret;
	(*argn)++;
	continue;
	}

	/* No test found. Interpret if as just a string. */
	update_val (args[*argn][0]);
	(*argn)++;
	}
	return ret;
	}

	static grub_err_t
	grub_cmd_test (grub_command_t cmd __attribute__ ((unused)),
	int argc, char **args)
	{
	int argn = 0;

	if (argc >= 1 && grub_strcmp (args[argc - 1], "]") == 0)
	argc--;

	return test_parse (args, &argn, argc) ? GRUB_ERR_NONE
	: grub_error (GRUB_ERR_TEST_FAILURE, N_("false"));
	}

	static grub_command_t cmd_1, cmd_2;

	GRUB_MOD_INIT(test)
	{
	cmd_1 = grub_register_command ("[", grub_cmd_test,
	N_("EXPRESSION ]"), N_("Evaluate an expression."));
	cmd_1->flags \|= GRUB_COMMAND_FLAG_EXTRACTOR;
	cmd_2 = grub_register_command ("test", grub_cmd_test,
	N_("EXPRESSION"), N_("Evaluate an expression."));
	cmd_2->flags \|= GRUB_COMMAND_FLAG_EXTRACTOR;
	}

	GRUB_MOD_FINI(test)
	{
	grub_unregister_command (cmd_1);
	grub_unregister_command (cmd_2);
	}