FLOCK
Section: Linux Programmer's Manual (2)
Updated: 22 July 1993
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NAME
flock - apply or remove an advisory lock on an open file
SYNOPSIS
#include <sys/file.h>
int flock(int fd, int operation)
DESCRIPTION
Apply or remove an advisory lock on an open file. The file is specified by
fd.
Valid operations are given below:
-
- LOCK_SH
-
Shared lock. More than one process may hold a shared lock for a given file
at a given time.
- LOCK_EX
-
Exclusive lock. Only one process may hold an exclusive lock for a given
file at a given time.
- LOCK_UN
-
Unlock.
- LOCK_NB
-
Don't block when locking. May be specified (by
or'ing)
along with one of the other operations.
A single file may not simultaneously have both shared and exclusive locks.
A file is locked (i.e., the inode),
not
the file descriptor. So,
dup(2)
and
fork(2)
do not create multiple instances of a lock.
RETURN VALUE
On success, zero is returned. On error, -1 is returned, and
errno
is set appropriately.
ERRORS
- EWOULDBLOCK
-
The file is locked an the
LOCK_NB
flag was selected.
NOTES
Under Linux,
flock
is implemented as a call to
fcntl.
Please see
fcntl(2)
for more details on errors.
SEE ALSO
open(2), close(2), dup(2), execve(2), fcntl(2),
fork(2),
Index
- NAME
-
- SYNOPSIS
-
- DESCRIPTION
-
- RETURN VALUE
-
- ERRORS
-
- NOTES
-
- SEE ALSO
-
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