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1 perry 1 LOCKF
2 !!!LOCKF
3 NAME
4 SYNOPSIS
5 DESCRIPTION
6 RETURN VALUE
7 ERRORS
8 CONFORMING TO
9 SEE ALSO
10 ----
11 !!NAME
12
13
14 lockf - apply, test or remove a POSIX lock on an open file
15 !!SYNOPSIS
16
17
18 __#include __
19
20
21 __int lockf(int__ fd__, int__ cmd__, off_t__
22 len__);__
23 !!DESCRIPTION
24
25
26 Apply, test or remove a POSIX lock on an open file. The file
27 is specified by ''fd''. This call is just an interface
28 for fcntl(2). Valid operations are given
29 below:
30
31
32 __F_LOCK__
33
34
35 Set an exclusive lock to the file. Only one process may hold
36 an exclusive lock for a given file at a given time. If the
37 file is already locked it blocks until the previous lock is
38 released.
39
40
41 __F_TLOCK__
42
43
44 Same as __F_LOCK__ but never blocks and return error
45 instead if the file is already locked.
46
47
48 __F_ULOCK__
49
50
51 Unlock the file.
52
53
54 __F_TEST__
55
56
57 Test the lock: return 0 if ''fd'' is unlocked or locked
58 by this process; return -1, set ''errno'' to
59 __EACCES__, if another process holds the
60 lock.
61 !!RETURN VALUE
62
63
64 On success, zero is returned. On error, -1 is returned, and
65 ''errno'' is set appropriately.
66 !!ERRORS
67
68
69 __EAGAIN__
70
71
72 The file is locked and the __LOCK_NB__ flag was selected,
73 or operation is prohibited because the file has been
74 memory-mapped by another process.
75
76
77 __EBADF__
78
79
80 ''fd'' is not an open file descriptor.
81
82
83 __EDEADLK__
84
85
86 Specified lock operation would cause a
87 deadlock.
88
89
90 __EINVAL__
91
92
93 An invalid operation was specified in
94 ''fd''.
95
96
97 __ENOLCK__
98
99
100 Too many segment locks open, lock table is
101 full.
102 !!CONFORMING TO
103
104
105 SYSV
106 !!SEE ALSO
107
108
109 fcntl(2), flock(2)
110 There are also ''locks.txt'' and ''mandatory.txt'' in
111 ''/usr/src/linux/Documentation''.
112 ----
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