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Add option to lockf to avoid creating a file if it does not exist.

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PR:	bin/170775
Submitted by:	Matthew Story <matthewstory@gmail.com>
Reviewed by:	scottl
MFC after:	1 week
This commit is contained in:
eadler 2013-05-10 17:30:29 +00:00
parent 4f9ab6c580
commit 93bce4ba3b
2 changed files with 28 additions and 8 deletions
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18
usr.bin/lockf/lockf.1
View File

@ -32,7 +32,7 @@
.Nd execute a command while holding a file lock
.Sh SYNOPSIS
.Nm
.Op Fl ks
.Op Fl kns
.Op Fl t Ar seconds
.Ar file
.Ar command
@ -90,6 +90,18 @@ Causes
.Nm
to operate silently.
Failure to acquire the lock is indicated only in the exit status.
.It Fl n
Causes
.Nm
to fail if the specified lock
.Ar file
does not exist. If
.Fl n
is not specified,
.Nm
will create
.Ar file
if necessary.
.It Fl t Ar seconds
Specifies a timeout for waiting for the lock.
By default,
@ -130,6 +142,10 @@ The
utility
was unable to create the lock file, e.g., because of insufficient access
privileges.
.It Dv EX_UNAVAILABLE
The
.Fl n
option is specified and the specified lock file does not exist.
.It Dv EX_USAGE
There was an error on the
.Nm

18
usr.bin/lockf/lockf.c
View File

@ -56,16 +56,20 @@ static volatile sig_atomic_t timed_out;
int
main(int argc, char **argv)
{
int ch, silent, status, waitsec;
int ch, flags, silent, status, waitsec;
pid_t child;
silent = keep = 0;
flags = O_CREAT;
waitsec = -1; /* Infinite. */
while ((ch = getopt(argc, argv, "skt:")) != -1) {
while ((ch = getopt(argc, argv, "sknt:")) != -1) {
switch (ch) {
case 'k':
keep = 1;
break;
case 'n':
flags &= ~O_CREAT;
break;
case 's':
silent = 1;
break;
@ -118,13 +122,13 @@ main(int argc, char **argv)
* avoiding the separate step of waiting for the lock. This
* yields fairness and improved performance.
*/
lockfd = acquire_lock(lockname, O_NONBLOCK);
lockfd = acquire_lock(lockname, flags | O_NONBLOCK);
while (lockfd == -1 && !timed_out && waitsec != 0) {
if (keep)
lockfd = acquire_lock(lockname, 0);
lockfd = acquire_lock(lockname, flags);
else {
wait_for_lock(lockname);
lockfd = acquire_lock(lockname, O_NONBLOCK);
lockfd = acquire_lock(lockname, flags | O_NONBLOCK);
}
}
if (waitsec > 0)
@ -165,7 +169,7 @@ acquire_lock(const char *name, int flags)
{
int fd;
if ((fd = open(name, O_RDONLY|O_CREAT|O_EXLOCK|flags, 0666)) == -1) {
if ((fd = open(name, flags|O_RDONLY|O_EXLOCK|flags, 0666)) == -1) {
if (errno == EAGAIN || errno == EINTR)
return (-1);
err(EX_CANTCREAT, "cannot open %s", name);
@ -215,7 +219,7 @@ usage(void)
{
fprintf(stderr,
"usage: lockf [-ks] [-t seconds] file command [arguments]\n");
"usage: lockf [-kns] [-t seconds] file command [arguments]\n");
exit(EX_USAGE);
}