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Manpage of LOCKF

LOCKF

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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