bash/builtins/command.def

This file is command.def, from which is created command.c.
It implements the builtin "command" in Bash.

Copyright (C) 1987-2008 Free Software Foundation, Inc.

This file is part of GNU Bash, the Bourne Again SHell.

Bash 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 2, or (at your option) any later
version.

Bash is distributed in the hope that it will be useful, but WITHOUT ANY
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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 Bash; see the file COPYING.  If not, write to the Free Software
Foundation, 59 Temple Place, Suite 330, Boston, MA 02111 USA.

$PRODUCES command.c

$BUILTIN command
$FUNCTION command_builtin
$SHORT_DOC command [-pVv] command [arg ...]
Execute a simple command or display information about commands.

Runs COMMAND with ARGS suppressing  shell function lookup, or display
information about the specified COMMANDs.  Can be used to invoke commands
on disk when a function with the same name exists.

Options:
  -p	use a default value for PATH that is guaranteed to find all of
	the standard utilities
  -v	print a description of COMMAND similar to the `type' builtin
  -V	print a more verbose description of each COMMAND

Exit Status:
Returns exit status of COMMAND, or failure if COMMAND is not found.
$END

#include <config.h>

#if defined (HAVE_UNISTD_H)
#  ifdef _MINIX
#    include <sys/types.h>
#  endif
#  include <unistd.h>
#endif

#include "../bashansi.h"

#include "../shell.h"
#include "../execute_cmd.h"
#include "../flags.h"
#include "bashgetopt.h"
#include "common.h"

#if defined (_CS_PATH) && defined (HAVE_CONFSTR) && !HAVE_DECL_CONFSTR
extern size_t confstr __P((int, char *, size_t));
#endif

extern int subshell_environment;

static void restore_path __P((char *));
static char *get_standard_path __P((void));

/* Run the commands mentioned in LIST without paying attention to shell
   functions. */
int
command_builtin (list)
     WORD_LIST *list;
{
  int result, verbose, use_standard_path, opt;
  char *old_path, *standard_path;
  COMMAND *command;

  verbose = use_standard_path = 0;
  reset_internal_getopt ();
  while ((opt = internal_getopt (list, "pvV")) != -1)
    {
      switch (opt)
	{
	case 'p':
	  use_standard_path = 1;
	  break;
	case 'V':
	  verbose = CDESC_SHORTDESC|CDESC_ABSPATH;	/* look in common.h for constants */
	  break;
	case 'v':
	  verbose = CDESC_REUSABLE;	/* ditto */
	  break;
	default:
	  builtin_usage ();
	  return (EX_USAGE);
	}
    }
  list = loptend;

  if (list == 0)
    return (EXECUTION_SUCCESS);

  if (verbose)
    {
      int found, any_found;

      for (any_found = 0; list; list = list->next)
	{
	  found = describe_command (list->word->word, verbose);

	  if (found == 0 && verbose != CDESC_REUSABLE)
	    sh_notfound (list->word->word);

	  any_found += found;
	}
      return (any_found ? EXECUTION_SUCCESS : EXECUTION_FAILURE);
    }

#if defined (RESTRICTED_SHELL)
  if (use_standard_path && restricted)
    {
      sh_restricted ("-p");
      return (EXECUTION_FAILURE);
    }
#endif

  begin_unwind_frame ("command_builtin");

  /* We don't want this to be reparsed (consider command echo 'foo &'), so
     just make a simple_command structure and call execute_command with it. */
  if (use_standard_path)
    {      
      old_path = get_string_value ("PATH");
      /* If old_path is NULL, $PATH is unset.  If so, we want to make sure
	 it's unset after this command completes. */
      if (old_path)
	old_path = savestring (old_path);
      add_unwind_protect ((Function *)restore_path, old_path);

      standard_path = get_standard_path ();
      bind_variable ("PATH", standard_path ? standard_path : "", 0);
      FREE (standard_path);
    }

#define COMMAND_BUILTIN_FLAGS (CMD_NO_FUNCTIONS | CMD_INHIBIT_EXPANSION | CMD_COMMAND_BUILTIN)

  command = make_bare_simple_command ();
  command->value.Simple->words = (WORD_LIST *)copy_word_list (list);
  command->value.Simple->redirects = (REDIRECT *)NULL;
  command->flags |= COMMAND_BUILTIN_FLAGS;
  command->value.Simple->flags |= COMMAND_BUILTIN_FLAGS;
#if 0
  /* This breaks for things like ( cd /tmp ; command z ababa ; echo next )
     or $(command echo a ; command echo b;) or even
     { command echo a; command echo b; } & */
  /* If we're in a subshell, see if we can get away without forking
     again, since we've already forked to run this builtin. */
  if (subshell_environment)
    {
      command->flags |= CMD_NO_FORK;
      command->value.Simple->flags |= CMD_NO_FORK;
    }
#endif
  add_unwind_protect ((char *)dispose_command, command);
  result = execute_command (command);

  run_unwind_frame ("command_builtin");

  return (result);
}

/* Restore the value of the $PATH variable after replacing it when
   executing `command -p'. */
static void
restore_path (var)
     char *var;
{
  if (var)
    {
      bind_variable ("PATH", var, 0);
      free (var);
    }
  else
    unbind_variable ("PATH");
}

/* Return a value for PATH that is guaranteed to find all of the standard
   utilities.  This uses Posix.2 configuration variables, if present.  It
   uses a value defined in config.h as a last resort. */
static char *
get_standard_path ()
{
#if defined (_CS_PATH) && defined (HAVE_CONFSTR)
  char *p;
  size_t len;

  len = (size_t)confstr (_CS_PATH, (char *)NULL, (size_t)0);
  if (len > 0)
    {
      p = (char *)xmalloc (len + 2);
      *p = '\0';
      confstr (_CS_PATH, p, len);
      return (p);
    }
  else
    return (savestring (STANDARD_UTILS_PATH));
#else /* !_CS_PATH || !HAVE_CONFSTR  */
#  if defined (CS_PATH)
  return (savestring (CS_PATH));
#  else
  return (savestring (STANDARD_UTILS_PATH));
#  endif /* !CS_PATH */
#endif /* !_CS_PATH || !HAVE_CONFSTR */
}