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