locking {
       # Default locker flags.
       flags arg;
       # Set timeout for acquiring the lock.
       retry-timeout arg;
       # Set the maximum number of times to retry acquiring the lock.
       retry-count number;
       # Expire locks older than this amount of time.
       expire-timeout number;
       # Use prog as external locker program.
       external-locker prog;
     }

— Configuration: flags string

Set locking flags. Argument is a string consisting of one or more of the following letters:

E

Use an external program to manage locks. The program is given by external-locker statement (see below).

R

If the locking attempt failed, retry it. This is the default. The number of retries, and time interval between the two successive attempts is given by retry-count and retry-timeout statements, correspondingly.

T

If a lock file exists, check its modification time and, if it is older than a predefined amount of time, remove the lock. The amount of time is specified by expire-timeout statement.

P

Store the PID of the locking process in a lock file.

— Configuration: retry-count number

Number of locking attempts. The ‘P’ flag must be set for this to take effect.

— Configuration: retry-timeout seconds

Time interval, in seconds, between the two successive locking attempts. The ‘P’ flag must be set for this to take effect.

— Configuration: expire-timeout seconds

Remove existing lock file, if it is created more than this number of seconds ago. The ‘T’ flag must be set for this to take effect.

— Configuration: external-locker string

Set command line of an external locker program. The ‘E’ flag must be set for this to take effect.