LOCKF
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Section: Linux Programmer's Manual (3)
Updated: 1997-08-06
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NAME
lockf - apply, test or remove a POSIX lock on an open file
SYNOPSIS
#include <sys/file.h>
int lockf(int fd, int cmd, off_t len);
DESCRIPTION
Apply, test or remove a POSIX lock on an open file. The file is specified by
fd.
This call is just an interface for
fcntl(2).
Valid operations are given below:
-
- F_LOCK
-
Set an exclusive lock to the file. Only one process may hold an exclusive
lock for a given file at a given time. If the file is already locked it
blocks until the previous lock is released.
- F_TLOCK
-
Same as
F_LOCK
but never blocks and return error instead if the file is
already locked.
- F_ULOCK
-
Unlock the file.
- F_TEST
-
Test the lock: return 0 if
fd
is unlocked or locked by this process; return -1, set
errno
to
EACCES,
if another process holds the lock.
RETURN VALUE
On success, zero is returned. On error, -1 is returned, and
errno
is set appropriately.
ERRORS
- EAGAIN
-
The file is locked and the
LOCK_NB
flag was selected, or operation is prohibited because the file has
been memory-mapped by another process.
- EBADF
-
fd
is not an open file descriptor.
- EDEADLK
-
Specified lock operation would cause a deadlock.
- EINVAL
-
An invalid operation was specified in
fd.
- ENOLCK
-
Too many segment locks open, lock table is full.
CONFORMING TO
SYSV
SEE ALSO
fcntl(2),
flock(2)
There are also
locks.txt
and
mandatory.txt
in
/usr/src/linux/Documentation.
Index
- NAME
-
- SYNOPSIS
-
- DESCRIPTION
-
- RETURN VALUE
-
- ERRORS
-
- CONFORMING TO
-
- SEE ALSO
-
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