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/*
* fq [FILES...] - follow output of nq jobs, quitting when they are done
*
* To the extent possible under law,
* Christian Neukirchen <chneukirchen@gmail.com>
* has waived all copyright and related or neighboring rights to this work.
* http://creativecommons.org/publicdomain/zero/1.0/
*/
#include <sys/file.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <errno.h>
#include <fcntl.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#define DELAY 250000
#ifdef __linux__
#define USE_INOTIFY
#endif
#ifdef USE_INOTIFY
#include <sys/inotify.h>
char ibuf[8192];
#endif
char buf[8192];
int
islocked(int fd)
{
if (flock(fd, LOCK_EX|LOCK_NB) == -1) {
return (errno == EWOULDBLOCK);
} else {
flock(fd, LOCK_UN);
return 0;
}
}
int
main(int argc, char *argv[])
{
int i, fd;
off_t off, loff;
ssize_t rd;
int didsth = 0;
#ifdef USE_INOTIFY
int ifd, wd;
#endif
close(0);
if (argc < 2) {
/* little better than glob(3)... */
execl("/bin/sh", "sh", "-c", "fq ${NQDIR:+$NQDIR/},*", (char *) 0);
exit(111);
}
#ifdef USE_INOTIFY
ifd = inotify_init();
if (ifd < 0)
exit(111);
#endif
for (i = 1; i < argc; i++) {
loff = 0;
fd = open(argv[i], O_RDONLY);
if (fd < 0)
continue;
/* skip not running jobs, unless we did not output anything yet
* and are at the last argument. */
if (!islocked(fd) && (didsth || i != argc - 1))
continue;
write(1, "==> ", 4);
write(1, argv[i], strlen(argv[i]));
write(1, "\n", 1);
didsth = 1;
#ifdef USE_INOTIFY
wd = inotify_add_watch(ifd, argv[i], IN_MODIFY|IN_CLOSE_WRITE);
#endif
while (1) {
off = lseek(fd, 0, SEEK_END);
if (off < loff)
loff = off; /* file truncated */
if (off == loff) {
if (flock(fd, LOCK_EX|LOCK_NB) == -1 &&
errno == EWOULDBLOCK) {
#ifdef USE_INOTIFY
/* any inotify event is good */
read(ifd, ibuf, sizeof ibuf);
#else
/* poll for size change */
while (off == lseek(fd, 0, SEEK_END))
usleep(DELAY);
#endif
continue;
} else {
flock(fd, LOCK_UN);
break;
}
}
if (off - loff > sizeof buf)
off = loff + sizeof buf;
rd = pread(fd, &buf, off - loff, loff);
write(1, buf, rd);
loff += rd;
}
#ifdef USE_INOTIFY
inotify_rm_watch(ifd, wd);
#endif
close(fd);
}
#ifdef USE_INOTIFY
close(ifd);
#endif
return 0;
}
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