| 1 | /* Test of select() substitute, reading from stdin.
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| 2 | Copyright (C) 2008 Free Software Foundation, Inc.
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| 3 |
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| 4 | This program is free software: you can redistribute it and/or modify
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| 5 | it under the terms of the GNU General Public License as published by
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| 6 | the Free Software Foundation; either version 3 of the License, or
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| 7 | (at your option) any later version.
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| 8 |
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| 9 | This program is distributed in the hope that it will be useful,
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| 10 | but WITHOUT ANY WARRANTY; without even the implied warranty of
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| 11 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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| 12 | GNU General Public License for more details.
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| 13 |
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| 14 | You should have received a copy of the GNU General Public License
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| 15 | along with this program. If not, see <http://www.gnu.org/licenses/>. */
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| 16 |
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| 17 | /* Written by Bruno Haible <bruno@clisp.org>, 2008. */
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| 18 |
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| 19 | #include <stdio.h>
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| 20 | #include <stdlib.h>
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| 21 | #include <sys/select.h>
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| 22 | #include <sys/time.h>
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| 23 | #include <unistd.h>
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| 24 |
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| 25 | int
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| 26 | main ()
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| 27 | {
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| 28 | printf ("Applying select() from standard input. Press Ctrl-C to abort.\n");
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| 29 | for (;;)
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| 30 | {
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| 31 | struct timeval before;
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| 32 | struct timeval after;
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| 33 | unsigned long spent_usec;
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| 34 | fd_set readfds;
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| 35 | struct timeval timeout;
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| 36 | int ret;
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| 37 |
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| 38 | gettimeofday (&before, NULL);
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| 39 |
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| 40 | FD_ZERO (&readfds);
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| 41 | FD_SET (0, &readfds);
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| 42 | timeout.tv_sec = 0;
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| 43 | timeout.tv_usec = 500000;
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| 44 | ret = select (1, &readfds, NULL, NULL, &timeout);
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| 45 |
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| 46 | gettimeofday (&after, NULL);
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| 47 | spent_usec = (after.tv_sec - before.tv_sec) * 1000000
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| 48 | + after.tv_usec - before.tv_usec;
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| 49 |
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| 50 | if (ret < 0)
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| 51 | {
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| 52 | perror ("select failed");
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| 53 | exit (1);
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| 54 | }
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| 55 | if ((ret == 0) != ! FD_ISSET (0, &readfds))
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| 56 | {
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| 57 | fprintf (stderr, "incorrect return value\n");
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| 58 | exit (1);
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| 59 | }
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| 60 | if (ret == 0)
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| 61 | {
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| 62 | if (spent_usec < 250000)
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| 63 | {
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| 64 | fprintf (stderr, "returned too early\n");
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| 65 | exit (1);
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| 66 | }
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| 67 | /* Timeout */
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| 68 | printf ("."); fflush (stdout);
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| 69 | }
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| 70 | else
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| 71 | {
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| 72 | char c;
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| 73 |
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| 74 | printf ("Input available! Trying to read 1 byte...\n");
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| 75 | read (0, &c, 1);
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| 76 | }
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| 77 | }
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| 78 | }
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