Linux 2.0
6 August 1997
manpages-pt-dev
Portuguese Versions of the Manual Pages (dev sections)
manpages-dev
Manual pages about using GNU/Linux for development
man-pages
Linux kernel and C library user-space interface documentation
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
