:sig
pid_t task_pid(String key)

:params
key : string uniquely identifying the task
return value : the process ID of the task

:desc
Checks whether a process with the given 'key' is running and returns its PID if it is. Returns 0 otherwise.

:see
>task

:related
**PHP:** Background-process patterns using `proc_open()`, queues, cron, or worker supervisors
**JavaScript / Node.js:** Node `child_process`, worker queues, timers, schedulers, and supervised background jobs