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popen2.m
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1999-04-14
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## Copyright (C) 1996, 1997 John W. Eaton
##
## This file is part of Octave.
##
## Octave 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.
##
## Octave 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 Octave; see the file COPYING. If not, write to the Free
## Software Foundation, 59 Temple Place - Suite 330, Boston, MA
## 02111-1307, USA.
## usage: [IN, OUT, PID] = popen2 (COMMAND, ARGS)
##
## Start a subprocess with two-way communication. COMMAND specifies
## the name of the command to start. ARGS is an array of strings
## containing options for COMMAND. IN and OUT are the file ids of the
## input and output streams for the subprocess, and PID is the process id of
## the subprocess, or -1 if COMMAND could not be executed.
##
## Example:
##
## [in, out, pid] = popen2 ("sort", "-nr");
## fputs (in, "these\n");
## fputs (in, "are\n");
## fputs (in, "some\n");
## fputs (in, "strings\n");
## fclose (in);
## while (isstr (s = fgets (out)))
## fputs (stdout, s);
## endwhile
## fclose (out);
## Author: Klaus Gebhardt, 1997
function [in, out, pid] = popen2 (command, args)
in = -1;
out = -1;
pid = -1;
if (nargin == 1 || nargin == 2)
if (isstr (command))
[r_pipe, r_status] = _pipe ();
[w_pipe, w_status] = _pipe ();
if ((r_status != -1) && (w_status != -1))
r_parent_end = r_pipe(1);
r_child_end = r_pipe(2);
_fcntl (r_parent_end, F_SETFD, 1);
r_org = _dup (1);
w_parent_end = w_pipe(2);
w_child_end = w_pipe(1);
_fcntl (w_parent_end, F_SETFD, 1);
w_org = _dup (0);
if ((r_org != -1) && (w_org != -1))
_dup2 (r_child_end, 1); _close (r_child_end); r_child_end = -1;
_dup2 (w_child_end, 0); _close (w_child_end); w_child_end = -1;
if (nargin == 1)
pid = spawn ("nowait", command);
else
pid = spawn ("nowait", command, args);
endif
_dup2 (r_org, 1); _close (r_org);
_dup2 (w_org, 0); _close (w_org);
endif
if (r_child_end != -1)
_close (r_child_end);
endif
if (w_child_end != -1)
_close (w_child_end);
endif
if (pid < 0)
_close (r_parent_end);
_close (w_parent_end);
error ("popen2: unable to start process `%s'", command);
else
out = _fdopen (r_parent_end, "r");
in = _fdopen (w_parent_end, "w");
endif
else
if (r_status != -1)
_close (r_pipe(1));
_close (r_pipe(2));
endif
if (wr_status != -1)
_close (w_pipe(1));
_close (w_pipe(2));
endif
error ("popen2: pipe creation failed");
endif
else
error ("popen2: file name must be a string");
endif
else
usage ("[in, out, pid] = popen2 (command, args)");
endif
endfunction