[mLib] / man / lock.3

.\" -*-nroff-*-
.TH lock 3 "23 May 1999" mLib
.SH NAME
lock \- oversimplified file locking interface
.\" @lock_file
.SH SYNOPSIS
.nf
.B "#include <mLib/lock.h>

.BI "int lock_file(int " fd ", unsigned " how );
.fi
.SH DESCRIPTION
The
.B lock_file
function provides an extremely simplistic interface to POSIX
.BR fcntl (2)
locking.  It locks only entire files, not sections of files.  It doesn't
have a nonblocking `is this file locked?' function.
.PP
On entry,
.I fd
should be a file descriptor on an open file, and
.I how
is a constant which describes how the file is to be locked.  The
possible values of
.I how
are:
.TP
.B LOCK_EXCL
Lock the file exclusively.  Attempts to lock the file exclusively or
nonexclusively will fail until the file is unlocked.
.TP
.B LOCK_NONEXCL
Lock the file nonexclusively.  Until the file is unlocked, attempts to
lock it exclusively will fail, but other nonexclusive locks will
succeed.
.TP
.B LOCK_UNLOCK
Unlocks a locked file.  Any locks afterwards can succeed.
.PP
The
.B lock_file
function will block if it can't obtain a lock immediately.  It will time
itself out after a short while (10 seconds in the current
implementation) if the lock doesn't become available.
.PP
If the call succeeds,
.B lock_file
returns zero.  On failure, \-1 is returned, and
.B errno
is set to an appropriate value.  Most of the error returns are from
.BR fcntl (2)
(q.v.).  If the lock operation times out,
.B errno
is set to
.BR EINTR .
.SH "SEE ALSO"
.BR fcntl (2),
.BR mLib (3).
.SH AUTHOR
Mark Wooding, <mdw@nsict.org>
Commit	Line	Data
b6b9d458	1	.\" --nroff--
08da152e	2	.TH lock 3 "23 May 1999" mLib
b6b9d458	3	.SH NAME
b6b9d458	4	lock \- oversimplified file locking interface
08da152e	5	.\" @lock_file
b6b9d458	6	.SH SYNOPSIS
	7	.nf
	8	.B "#include <mLib/lock.h>
	9
	10	.BI "int lock_file(int " fd ", unsigned " how );
	11	.fi
	12	.SH DESCRIPTION
	13	The
	14	.B lock_file
	15	function provides an extremely simplistic interface to POSIX
	16	.BR fcntl (2)
	17	locking. It locks only entire files, not sections of files. It doesn't
	18	have a nonblocking `is this file locked?' function.
	19	.PP
	20	On entry,
	21	.I fd
	22	should be a file descriptor on an open file, and
	23	.I how
	24	is a constant which describes how the file is to be locked. The
	25	possible values of
	26	.I how
	27	are:
	28	.TP
	29	.B LOCK_EXCL
	30	Lock the file exclusively. Attempts to lock the file exclusively or
	31	nonexclusively will fail until the file is unlocked.
	32	.TP
	33	.B LOCK_NONEXCL
	34	Lock the file nonexclusively. Until the file is unlocked, attempts to
	35	lock it exclusively will fail, but other nonexclusive locks will
	36	succeed.
	37	.TP
	38	.B LOCK_UNLOCK
	39	Unlocks a locked file. Any locks afterwards can succeed.
	40	.PP
	41	The
	42	.B lock_file
	43	function will block if it can't obtain a lock immediately. It will time
	44	itself out after a short while (10 seconds in the current
	45	implementation) if the lock doesn't become available.
	46	.PP
	47	If the call succeeds,
	48	.B lock_file
	49	returns zero. On failure, \-1 is returned, and
	50	.B errno
	51	is set to an appropriate value. Most of the error returns are from
	52	.BR fcntl (2)
	53	(q.v.). If the lock operation times out,
	54	.B errno
	55	is set to
	56	.BR EINTR .
08da152e	57	.SH "SEE ALSO"
	58	.BR fcntl (2),
	59	.BR mLib (3).
b6b9d458	60	.SH AUTHOR
b6b9d458	61	Mark Wooding, <mdw@nsict.org>