1  /* Test of select() substitute, reading or writing from a given file descriptor.
       2     Copyright (C) 2008-2022 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  }