/* gshell.c - Shell-related utilities

 *

 *  Copyright 2000 Red Hat, Inc.

 *  g_execvpe implementation based on GNU libc execvp:

 *   Copyright 1991, 92, 95, 96, 97, 98, 99 Free Software Foundation, Inc.

 * Portions copyright (c) 2006-2009 Nokia Corporation.  All rights reserved.

 *

 * GLib is free software; you can redistribute it and/or

 * modify it under the terms of the GNU Lesser General Public License as

 * published by the Free Software Foundation; either version 2 of the

 * License, or (at your option) any later version.

 *

 * GLib 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

 * Lesser General Public License for more details.

 *

 * You should have received a copy of the GNU Lesser General Public

 * License along with GLib; 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 "config.h"

#include <string.h>

#include "glib.h"

#ifdef _

#warning "FIXME remove gettext hack"

#endif

#include "glibintl.h"

#include "galias.h"

EXPORT_C GQuark

g_shell_error_quark (void)

{

  return g_quark_from_static_string ("g-shell-error-quark");

}

/* Single quotes preserve the literal string exactly. escape

 * sequences are not allowed; not even \' - if you want a '

 * in the quoted text, you have to do something like 'foo'\''bar'

 *

 * Double quotes allow $ ` " \ and newline to be escaped with backslash.

 * Otherwise double quotes preserve things literally.

 */

static gboolean 

unquote_string_inplace (gchar* str, gchar** end, GError** err)

{

  gchar* dest;

  gchar* s;

  gchar quote_char;

  g_return_val_if_fail(end != NULL, FALSE);

  g_return_val_if_fail(err == NULL || *err == NULL, FALSE);

  g_return_val_if_fail(str != NULL, FALSE);

  dest = s = str;

  quote_char = *s;

  if (!(*s == '"' || *s == '\''))

    {

      g_set_error_literal (err,

                           G_SHELL_ERROR,

                           G_SHELL_ERROR_BAD_QUOTING,

                           _("Quoted text doesn't begin with a quotation mark"));

      *end = str;

      return FALSE;

    }

  /* Skip the initial quote mark */

  ++s;

  if (quote_char == '"')

    {

      while (*s)

        {

          g_assert(s > dest); /* loop invariant */

          switch (*s)

            {

            case '"':

              /* End of the string, return now */

              *dest = '\0';

              ++s;

              *end = s;

              return TRUE;

              break;

            case '\\':

              /* Possible escaped quote or \ */

              ++s;

              switch (*s)

                {

                case '"':

                case '\\':

                case '`':

                case '$':

                case '\n':

                  *dest = *s;

                  ++s;

                  ++dest;

                  break;

                default:

                  /* not an escaped char */

                  *dest = '\\';

                  ++dest;

                  /* ++s already done. */

                  break;

                }

              break;

            default:

              *dest = *s;

              ++dest;

              ++s;

              break;

            }

          g_assert(s > dest); /* loop invariant */

        }

    }

  else

    {

      while (*s)

        {

          g_assert(s > dest); /* loop invariant */

          if (*s == '\'')

            {

              /* End of the string, return now */

              *dest = '\0';

              ++s;

              *end = s;

              return TRUE;

            }

          else

            {

              *dest = *s;

              ++dest;

              ++s;

            }

          g_assert(s > dest); /* loop invariant */

        }

    }

  /* If we reach here this means the close quote was never encountered */

  *dest = '\0';

  g_set_error_literal (err,

                       G_SHELL_ERROR,

                       G_SHELL_ERROR_BAD_QUOTING,

                       _("Unmatched quotation mark in command line or other shell-quoted text"));

  *end = s;

  return FALSE;

}

/**

 * g_shell_quote:

 * @unquoted_string: a literal string

 * 

 * Quotes a string so that the shell (/bin/sh) will interpret the

 * quoted string to mean @unquoted_string. If you pass a filename to

 * the shell, for example, you should first quote it with this

 * function.  The return value must be freed with g_free(). The

 * quoting style used is undefined (single or double quotes may be

 * used).

 * 

 * Return value: quoted string

 **/

EXPORT_C gchar*

g_shell_quote (const gchar *unquoted_string)

{

  /* We always use single quotes, because the algorithm is cheesier.

   * We could use double if we felt like it, that might be more

   * human-readable.

   */

  const gchar *p;

  GString *dest;

  g_return_val_if_fail (unquoted_string != NULL, NULL);

  dest = g_string_new ("'");

  p = unquoted_string;

  /* could speed this up a lot by appending chunks of text at a

   * time.

   */

  while (*p)

    {

      /* Replace literal ' with a close ', a \', and a open ' */

      if (*p == '\'')

        g_string_append (dest, "'\\''");

      else

        g_string_append_c (dest, *p);

      ++p;

    }

  /* close the quote */

  g_string_append_c (dest, '\'');

  return g_string_free (dest, FALSE);

}

/**

 * g_shell_unquote:

 * @quoted_string: shell-quoted string

 * @error: error return location or NULL

 * 

 * Unquotes a string as the shell (/bin/sh) would. Only handles

 * quotes; if a string contains file globs, arithmetic operators,

 * variables, backticks, redirections, or other special-to-the-shell

 * features, the result will be different from the result a real shell

 * would produce (the variables, backticks, etc. will be passed

 * through literally instead of being expanded). This function is

 * guaranteed to succeed if applied to the result of

 * g_shell_quote(). If it fails, it returns %NULL and sets the

 * error. The @quoted_string need not actually contain quoted or

 * escaped text; g_shell_unquote() simply goes through the string and

 * unquotes/unescapes anything that the shell would. Both single and

 * double quotes are handled, as are escapes including escaped

 * newlines. The return value must be freed with g_free(). Possible

 * errors are in the #G_SHELL_ERROR domain.

 * 

 * Shell quoting rules are a bit strange. Single quotes preserve the

 * literal string exactly. escape sequences are not allowed; not even

 * \' - if you want a ' in the quoted text, you have to do something

 * like 'foo'\''bar'.  Double quotes allow $, `, ", \, and newline to

 * be escaped with backslash. Otherwise double quotes preserve things

 * literally.

 *

 * Return value: an unquoted string

 **/

EXPORT_C gchar*

g_shell_unquote (const gchar *quoted_string,

                 GError     **error)

{

  gchar *unquoted;

  gchar *end;

  gchar *start;

  GString *retval;

  g_return_val_if_fail (quoted_string != NULL, NULL);

  unquoted = g_strdup (quoted_string);

  start = unquoted;

  end = unquoted;

  retval = g_string_new (NULL);

  /* The loop allows cases such as

   * "foo"blah blah'bar'woo foo"baz"la la la\'\''foo'

   */

  while (*start)

    {

      /* Append all non-quoted chars, honoring backslash escape

       */

      while (*start && !(*start == '"' || *start == '\''))

        {

          if (*start == '\\')

            {

              /* all characters can get escaped by backslash,

               * except newline, which is removed if it follows

               * a backslash outside of quotes

               */

              ++start;

              if (*start)

                {

                  if (*start != '\n')

                    g_string_append_c (retval, *start);

                  ++start;

                }

            }

          else

            {

              g_string_append_c (retval, *start);

              ++start;

            }

        }

      if (*start)

        {

          if (!unquote_string_inplace (start, &end, error))

            {

              goto error;

            }

          else

            {

              g_string_append (retval, start);

              start = end;

            }

        }

    }

  g_free (unquoted);

  return g_string_free (retval, FALSE);

 error:

  g_assert (error == NULL || *error != NULL);

  g_free (unquoted);

  g_string_free (retval, TRUE);

  return NULL;

}

/* g_parse_argv() does a semi-arbitrary weird subset of the way

 * the shell parses a command line. We don't do variable expansion,

 * don't understand that operators are tokens, don't do tilde expansion,

 * don't do command substitution, no arithmetic expansion, IFS gets ignored,

 * don't do filename globs, don't remove redirection stuff, etc.

 *

 * READ THE UNIX98 SPEC on "Shell Command Language" before changing

 * the behavior of this code.

 *

 * Steps to parsing the argv string:

 *

 *  - tokenize the string (but since we ignore operators,

 *    our tokenization may diverge from what the shell would do)

 *    note that tokenization ignores the internals of a quoted

 *    word and it always splits on spaces, not on IFS even

 *    if we used IFS. We also ignore "end of input indicator"

 *    (I guess this is control-D?)

 *

 *    Tokenization steps, from UNIX98 with operator stuff removed,

 *    are:

 * 

 *    1) "If the current character is backslash, single-quote or

 *        double-quote (\, ' or ") and it is not quoted, it will affect

 *        quoting for subsequent characters up to the end of the quoted

 *        text. The rules for quoting are as described in Quoting

 *        . During token recognition no substitutions will be actually

 *        performed, and the result token will contain exactly the

 *        characters that appear in the input (except for newline

 *        character joining), unmodified, including any embedded or

 *        enclosing quotes or substitution operators, between the quote

 *        mark and the end of the quoted text. The token will not be

 *        delimited by the end of the quoted field."

 *

 *    2) "If the current character is an unquoted newline character,

 *        the current token will be delimited."

 *

 *    3) "If the current character is an unquoted blank character, any

 *        token containing the previous character is delimited and the

 *        current character will be discarded."

 *

 *    4) "If the previous character was part of a word, the current

 *        character will be appended to that word."

 *

 *    5) "If the current character is a "#", it and all subsequent

 *        characters up to, but excluding, the next newline character

 *        will be discarded as a comment. The newline character that

 *        ends the line is not considered part of the comment. The

 *        "#" starts a comment only when it is at the beginning of a

 *        token. Since the search for the end-of-comment does not

 *        consider an escaped newline character specially, a comment

 *        cannot be continued to the next line."

 *

 *    6) "The current character will be used as the start of a new word."

 *

 *

 *  - for each token (word), perform portions of word expansion, namely

 *    field splitting (using default whitespace IFS) and quote

 *    removal.  Field splitting may increase the number of words.

 *    Quote removal does not increase the number of words.

 *

 *   "If the complete expansion appropriate for a word results in an

 *   empty field, that empty field will be deleted from the list of

 *   fields that form the completely expanded command, unless the

 *   original word contained single-quote or double-quote characters."

 *    - UNIX98 spec

 *

 *

 */

static inline void

ensure_token (GString **token)

{

  if (*token == NULL)

    *token = g_string_new (NULL);

}

static void

delimit_token (GString **token,

               GSList **retval)

{

  if (*token == NULL)

    return;

  *retval = g_slist_prepend (*retval, g_string_free (*token, FALSE));

  *token = NULL;

}

static GSList*

tokenize_command_line (const gchar *command_line,

                       GError **error)

{

  gchar current_quote;

  const gchar *p;

  GString *current_token = NULL;

  GSList *retval = NULL;

  gboolean quoted;;

  current_quote = '\0';

  quoted = FALSE;

  p = command_line;

  while (*p)

    {

      if (current_quote == '\\')

        {

          if (*p == '\n')

            {

              /* we append nothing; backslash-newline become nothing */

            }

          else

            {

              /* we append the backslash and the current char,

               * to be interpreted later after tokenization

               */

              ensure_token (&current_token);

              g_string_append_c (current_token, '\\');

              g_string_append_c (current_token, *p);

            }

          current_quote = '\0';

        }

      else if (current_quote == '#')

        {

          /* Discard up to and including next newline */

          while (*p && *p != '\n')

            ++p;

          current_quote = '\0';

          if (*p == '\0')

            break;

        }

      else if (current_quote)

        {

          if (*p == current_quote &&

              /* check that it isn't an escaped double quote */

              !(current_quote == '"' && quoted))

            {

              /* close the quote */

              current_quote = '\0';

            }

          /* Everything inside quotes, and the close quote,

           * gets appended literally.

           */

          ensure_token (&current_token);

          g_string_append_c (current_token, *p);

        }

      else

        {

          switch (*p)

            {

            case '\n':

              delimit_token (&current_token, &retval);

              break;

            case ' ':

            case '\t':

              /* If the current token contains the previous char, delimit

               * the current token. A nonzero length

               * token should always contain the previous char.

               */

              if (current_token &&

                  current_token->len > 0)

                {

                  delimit_token (&current_token, &retval);

                }

              /* discard all unquoted blanks (don't add them to a token) */

              break;

              /* single/double quotes are appended to the token,

               * escapes are maybe appended next time through the loop,

               * comment chars are never appended.

               */

            case '\'':

            case '"':

              ensure_token (&current_token);

              g_string_append_c (current_token, *p);

              /* FALL THRU */

            case '#':

            case '\\':

              current_quote = *p;

              break;

            default:

              /* Combines rules 4) and 6) - if we have a token, append to it,

               * otherwise create a new token.

               */

              ensure_token (&current_token);

              g_string_append_c (current_token, *p);

              break;

            }

        }

      /* We need to count consecutive backslashes mod 2, 

       * to detect escaped doublequotes.

       */

      if (*p != '\\')

	quoted = FALSE;

      else

	quoted = !quoted;

      ++p;