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PERL flock Function
Syntax
flock FILEHANDLE, OPERATION
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Definition and Usage
Supports file locking on the specified FILEHANDLE using the system flock( ), fcntl( )
locking, or lockf( ). The exact implementation used is dependent on what your system
supports. OPERATION is one of the static values defined here...
Operation Result
LOCK_SH Set shared lock.
LOCK_EX Set exclusive lock.
LOCK_UN Unlock specified file.
LONG_NB Set lock without blocking.
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Return Value
Example
Following are the usage...
Here's a mailbox appender for BSD systems:
use Fcntl ':flock'; # import LOCK_* constants
sub lock {
flock(MBOX,LOCK_EX);
# and, in case someone appended
# while we were waiting...
seek(MBOX, 0, 2);
}
sub unlock {
flock(MBOX,LOCK_UN);
}
open(MBOX, ">>/usr/spool/mail/$ENV{'USER'}")
or die "Can't open mailbox: $!";
lock();
print MBOX $msg,"\n\n";
unlock();
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