tests/test-select-fd.c

   1 /* Test of select() substitute, reading or writing from a given file descriptor.
   2    Copyright (C) 2008-2024 Free Software Foundation, Inc.
   3
   4    This program is free software: you can redistribute it and/or modify
   5    it under the terms of the GNU General Public License as published by
   6    the Free Software Foundation, either version 3 of the License, or
   7    (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 /* Written by Bruno Haible <bruno@clisp.org>, 2008.  */
  18
  19 #include <config.h>
  20
  21 #include <stdio.h>
  22 #include <stdlib.h>
  23 #include <sys/select.h>
  24
  25 int
  26 main (int argc, char *argv[])
  27 {
  28   if (argc == 4)
  29     {
  30       char mode = argv[1][0];
  31
  32       if (mode == 'r' || mode == 'w')
  33         {
  34           int fd = atoi (argv[2]);
  35
  36           if (fd >= 0)
  37             {
  38               const char *result_file_name = argv[3];
  39               FILE *result_file = fopen (result_file_name, "wb");
  40
  41               if (result_file != NULL)
  42                 {
  43                   fd_set fds;
  44                   struct timeval timeout;
  45                   int ret;
  46
  47                   FD_ZERO (&fds);
  48                   FD_SET (fd, &fds);
  49                   timeout.tv_sec = 0;
  50                   timeout.tv_usec = 10000;
  51                   ret = (mode == 'r'
  52                          ? select (fd + 1, &fds, NULL, NULL, &timeout)
  53                          : select (fd + 1, NULL, &fds, NULL, &timeout));
  54                   if (ret < 0)
  55                     {
  56                       perror ("select failed");
  57                       exit (1);
  58                     }
  59                   if ((ret == 0) != ! FD_ISSET (fd, &fds))
  60                     {
  61                       fprintf (stderr, "incorrect return value\n");
  62                       exit (1);
  63                     }
  64                   fprintf (result_file, "%d\n", ret);
  65                   exit (0);
  66                 }
  67             }
  68         }
  69     }
  70   fprintf (stderr, "Usage: test-select-fd mode fd result-file-name\n");
  71   exit (1);
  72 }