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LOCKF
!!!LOCKF
NAME
SYNOPSIS
DESCRIPTION
RETURN VALUE
ERRORS
CONFORMING TO
SEE ALSO
----
!!NAME


lockf - apply, test or remove a POSIX lock on an open file
!!SYNOPSIS


__#include __


__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''.
----

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Last edited on Tuesday, June 4, 2002 12:24:27 am by "perry"

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