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/*
* fspause.c: pause until a file timestamp updates
*
* Copyright (C) 2014 Colin Watson.
*
* This file is part of man-db.
*
* man-db is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* man-db is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with man-db; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
*/
#ifdef HAVE_CONFIG_H
# include "config.h"
#endif /* HAVE_CONFIG_H */
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <time.h>
#include <unistd.h>
#include "attribute.h"
#include "progname.h"
#include "stat-time.h"
#include "timespec.h"
#include "xalloc.h"
#include "manconfig.h"
static char *filename;
static int fd = -1;
#define MUST(name, cond) \
do { \
if (!(cond)) { \
fprintf (stderr, "fspause: " name " failed\n"); \
abort (); \
} \
} while (0)
static void unlink_tempfile (void)
{
if (fd >= 0) {
MUST ("close", close (fd) >= 0);
MUST ("unlink", unlink (filename) >= 0);
}
}
static void delay (int delay_ns)
{
struct timespec delay_ts;
delay_ts.tv_sec = delay_ns / 1000000000;
delay_ts.tv_nsec = delay_ns % 1000000000;
for (;;) {
errno = 0;
if (nanosleep (&delay_ts, NULL) == 0)
break;
MUST ("nanosleep", errno == 0 || errno == EINTR);
}
}
static int try_delay (struct stat *st, int delay_ns)
{
struct timespec start_ts, end_ts;
start_ts = get_stat_mtime (st);
delay (delay_ns);
MUST ("write", write (fd, "\n", 1) == 1);
MUST ("fstat", fstat (fd, st) >= 0);
end_ts = get_stat_mtime (st);
return timespec_cmp (start_ts, end_ts) != 0;
}
int main (int argc MAYBE_UNUSED, char **argv)
{
struct stat st;
int delay_ns;
set_program_name (argv[0]);
filename = xstrdup ("fspause.tmp.XXXXXX");
MUST ("mkstemp", (fd = mkstemp (filename)) >= 0);
atexit (unlink_tempfile);
MUST ("fstat", fstat (fd, &st) >= 0);
/* 0x40000000 nanoseconds is just over a second. The effective
* maximum delay we will allow is thus about two seconds. This
* saves us having to keep track of anything more complicated than a
* single signed 32-bit int.
*/
for (delay_ns = 1; delay_ns < 0x40000000; delay_ns *= 2) {
if (try_delay (&st, delay_ns))
return 0;
}
fprintf (stderr,
"fspause: temporary file timestamp refuses to change!\n");
return 1;
}
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