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ae77ce91c8
Without _GNU_SOURCE defined this file fails to compile with the
following error:
$ gcc manual/examples/select.c
manual/examples/select.c: In function ‘input_timeout’:
manual/examples/select.c:44:10: error: implicit declaration of function ‘TEMP_FAILURE_RETRY’ [-Wimplicit-function-declaration]
44 | return TEMP_FAILURE_RETRY (select (FD_SETSIZE,
| ^~~~~~~~~~~~~~~~~~
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
60 lines
1.5 KiB
C
60 lines
1.5 KiB
C
/* Waiting for Input or Output
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Copyright (C) 1991-2025 Free Software Foundation, Inc.
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This program is free software; you can redistribute it and/or
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modify it under the terms of the GNU General Public License
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as published by the Free Software Foundation; either version 2
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of the License, or (at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, see <https://www.gnu.org/licenses/>.
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*/
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/*@group*/
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#define _GNU_SOURCE 1
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#include <errno.h>
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#include <stdio.h>
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#include <unistd.h>
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#include <sys/types.h>
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#include <sys/select.h>
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/*@end group*/
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/*@group*/
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int
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input_timeout (int filedes, unsigned int seconds)
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{
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fd_set set;
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struct timeval timeout;
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/*@end group*/
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/* Initialize the file descriptor set. */
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FD_ZERO (&set);
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FD_SET (filedes, &set);
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/* Initialize the timeout data structure. */
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timeout.tv_sec = seconds;
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timeout.tv_usec = 0;
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/*@group*/
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/* @code{select} returns 0 if timeout, 1 if input available, -1 if error. */
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return TEMP_FAILURE_RETRY (select (FD_SETSIZE,
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&set, NULL, NULL,
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&timeout));
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}
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/*@end group*/
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/*@group*/
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int
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main (void)
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{
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fprintf (stderr, "select returned %d.\n",
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input_timeout (STDIN_FILENO, 5));
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return 0;
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}
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/*@end group*/
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