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The trigger-listen Program

Usage

Description

The trigger-listen program listens for input on the fifo path. When it receives input trigger-listen invokes prog and continues to listen for input on path. An external program pulls the trigger by writing a byte of data to path.

General Options

• -q: Quiet. Do not print error messages.
• -Q: (Default) Print error messages.
• -v: Verbose. Print both status and error messages.

Listening Options

• -1: Execute prog immediately upon startup.
• -c limit: Execute at most limit copies of prog concurrently. If a trigger pull occurs while limit copies are running, trigger-listen executes prog as soon as one of the running copies exits.
• -t timeout: Wait at most timeout seconds for a trigger pull. If timeout seconds elapse without a trigger pull, then trigger-listen pulls its own trigger. The default value of timeout is (unsigned int)~0.
• -i interval: Wait at least interval seconds between executions of prog. If it receives a trigger pull within interval seconds of the last execution, trigger-listen executes prog when interval seconds have elapsed. The default value of interval is 0.
• -g gid: Switch group ID to gid after preparing to receive trigger pulls.
• -u uid: Switch user ID to uid after preparing to receive connections.
• -U: Same as -g $GID -u $UID. Typically, $GID and $UID are set by ttp://cr.yp.to/daemontools/envuidgid.htmlenvuidgid.
• -d: (Default) Delete. Remove and recreate the fifo path upon startup.
• -D: No delete. Do not remove and recreate path upon startup.

Errors

The trigger-listen exits 111 for temporary errors and 100 for permanent errors.