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## Copyright (C) 1996 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 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: jwe
function [in, out, pid] = popen2 (command, args)
in = -1;
out = -1;
pid = -1;
if (nargin == 1 || nargin == 2)
if (nargin == 1)
args = "";
endif
if (isstr (command))
[stdin_pipe, stdin_status] = pipe ();
[stdout_pipe, stdout_status] = pipe ();
if (stdin_status == 0 && stdout_status == 0)
pid = fork ();
if (pid == 0)
fclose (stdin_pipe (2));
fclose (stdout_pipe (1));
dup2 (stdin_pipe (1), stdin);
fclose (stdin_pipe (1));
dup2 (stdout_pipe (2), stdout);
fclose (stdout_pipe (2));
if (exec (command, args) < 0)
error ("popen2: unable to start process `%s'", command);
exit (0);
endif
elseif (pid)
fclose (stdin_pipe (1));
fclose (stdout_pipe (2));
if (fcntl (stdout_pipe (1), __F_SETFL__, __O_NONBLOCK__) < 0)
error ("popen2: error setting file mode");
else
in = stdin_pipe (2);
out = stdout_pipe (1);
endif
elseif (pid < 0)
error ("popen2: fork failed -- unable to create child process");
endif
else
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
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