manual/examples/popen.c

   1 /* Pipe to a Subprocess
   2    Copyright (C) 1991-2021 Free Software Foundation, Inc.
   3
   4    This program is free software; you can redistribute it and/or
   5    modify it under the terms of the GNU General Public License
   6    as published by the Free Software Foundation; either version 2
   7    of the License, or (at your option) any later version.
   8
   9    This program is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12    GNU General Public License for more details.
  13
  14    You should have received a copy of the GNU General Public License
  15    along with this program; if not, see <https://www.gnu.org/licenses/>.
  16 */
  17
  18 #include <stdio.h>
  19 #include <stdlib.h>
  20
  21 void
  22 write_data (FILE * stream)
  23 {
  24   int i;
  25   for (i = 0; i < 100; i++)
  26     fprintf (stream, "%d\n", i);
  27   if (ferror (stream))
  28     {
  29       fprintf (stderr, "Output to stream failed.\n");
  30       exit (EXIT_FAILURE);
  31     }
  32 }
  33
  34 /*@group*/
  35 int
  36 main (void)
  37 {
  38   FILE *output;
  39
  40   output = popen ("more", "w");
  41   if (!output)
  42     {
  43       fprintf (stderr,
  44                "incorrect parameters or too many files.\n");
  45       return EXIT_FAILURE;
  46     }
  47   write_data (output);
  48   if (pclose (output) != 0)
  49     {
  50       fprintf (stderr,
  51                "Could not run more or other error.\n");
  52     }
  53   return EXIT_SUCCESS;
  54 }
  55 /*@end group*/