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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:
Eitan Adler 2013-05-10 17:30:29 +00:00
parent 7a2b450ff8
commit b5be420a7c
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=250462
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 .Nd execute a command while holding a file lock
.Sh SYNOPSIS .Sh SYNOPSIS
.Nm .Nm
.Op Fl ks .Op Fl kns
.Op Fl t Ar seconds .Op Fl t Ar seconds
.Ar file .Ar file
.Ar command .Ar command
@ -90,6 +90,18 @@ Causes
.Nm .Nm
to operate silently. to operate silently.
Failure to acquire the lock is indicated only in the exit status. 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 .It Fl t Ar seconds
Specifies a timeout for waiting for the lock. Specifies a timeout for waiting for the lock.
By default, By default,
@ -130,6 +142,10 @@ The
utility utility
was unable to create the lock file, e.g., because of insufficient access was unable to create the lock file, e.g., because of insufficient access
privileges. privileges.
.It Dv EX_UNAVAILABLE
The
.Fl n
option is specified and the specified lock file does not exist.
.It Dv EX_USAGE .It Dv EX_USAGE
There was an error on the There was an error on the
.Nm .Nm

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

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