xapian-applications/omega/runfilter.h

   1 /* runfilter.h: run an external filter and capture its output in a std::string.
   2  *
   3  * Copyright (C) 2007,2013,2015 Olly Betts
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License as published by
   7  * the Free Software Foundation; either version 2 of the License, or
   8  * (at your option) any later version.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13  * GNU General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License
  16  * along with this program; if not, write to the Free Software
  17  * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301 USA
  18  */
  19
  20 #ifndef OMEGA_INCLUDED_RUNFILTER_H
  21 #define OMEGA_INCLUDED_RUNFILTER_H
  22
  23 #include <string>
  24 #include <cstdio>
  25
  26 /// Exception thrown if we encounter a read error.
  27 struct ReadError {
  28     const char * msg;
  29     int status;
  30     explicit ReadError(const char * m) : msg(m) { }
  31     explicit ReadError(int s) : msg(NULL), status(s) { }
  32     std::string str() const { if (msg) return msg; char buf[32]; std::sprintf(buf, "0x%08x", status); return buf; }
  33 };
  34
  35 /// Exception thrown if the filter program isn't found.
  36 struct NoSuchFilter { };
  37
  38 /** Analyse if a command needs the shell.
  39  *
  40  *  The return value of this function can be passed as the second argument of
  41  *  stdout_to_string().
  42  */
  43 bool command_needs_shell(const char * p);
  44
  45 /// Initialise the runfilter module.
  46 void runfilter_init();
  47
  48 /** Run command @a cmd, capture its stdout, and return it as a std::string.
  49  *
  50  *  @param use_shell  If false, try to avoid using a shell to run the command.
  51  *  @param alt_status   Exit status to treat as success in addition to 0
  52  *                      (default: Only treat exit status 0 as success).
  53  *
  54  *  Note: use_shell=false mode makes some assumptions about the command:
  55  *
  56  *  * only single quotes are used (double quotes and backslash quoting are
  57  *    not currently handled, aside from in the four character sequence '\''
  58  *    within single quotes).
  59  *  * the following redirections are supported, but they must be unquoted and
  60  *    appear exactly as shown, and each be a separate word in the command:
  61  *    >/dev/null 2>/dev/null 2>&1 1>&2
  62  *  * environment variables set before the command are handled correctly,
  63  *    for example: LANG=C some-command
  64  *
  65  *  The command_needs_shell() function above can be used to check a command,
  66  *  but is somewhat more conservative than what this function actually
  67  *  supports.
  68  *
  69  *  Currently the shell is only actually avoided for systems with both fork()
  70  *  and socketpair().  Other systems will ignore use_shell and always use the
  71  *  same code path (which may or may not involve some analog of the Unix
  72  *  shell).
  73  */
  74 std::string stdout_to_string(const std::string &cmd, bool use_shell,
  75                              int alt_status = 0);
  76
  77 #endif // OMEGA_INCLUDED_RUNFILTER_H