1  /* Waiting for Input or Output
       2     Copyright (C) 1991-2023 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  /*@group*/
      19  #include <errno.h>
      20  #include <stdio.h>
      21  #include <unistd.h>
      22  #include <sys/types.h>
      23  #include <sys/time.h>
      24  /*@end group*/
      25  
      26  /*@group*/
      27  int
      28  input_timeout (int filedes, unsigned int seconds)
      29  {
      30    fd_set set;
      31    struct timeval timeout;
      32  /*@end group*/
      33  
      34    /* Initialize the file descriptor set. */
      35    FD_ZERO (&set);
      36    FD_SET (filedes, &set);
      37  
      38    /* Initialize the timeout data structure. */
      39    timeout.tv_sec = seconds;
      40    timeout.tv_usec = 0;
      41  
      42  /*@group*/
      43    /* @code{select} returns 0 if timeout, 1 if input available, -1 if error. */
      44    return TEMP_FAILURE_RETRY (select (FD_SETSIZE,
      45  				     &set, NULL, NULL,
      46  				     &timeout));
      47  }
      48  /*@end group*/
      49  
      50  /*@group*/
      51  int
      52  main (void)
      53  {
      54    fprintf (stderr, "select returned %d.\n",
      55  	   input_timeout (STDIN_FILENO, 5));
      56    return 0;
      57  }
      58  /*@end group*/