In Unix shells, <code>wait</code> is a command which pauses until execution of a background process has ended.
where n... is a list of pids or job IDs of a currently executing background process (job). If no ids are provided, the command waits until all jobs known to the invoking shell have terminated.
wait normally returns the exit status of the last job which terminated. It may also return 127 in the event that n specifies a non-existent job or zero if there were no jobs to wait for.
Because <code>wait</code> needs to be aware of the job table of the current shell execution environment. Under the POSIX specifications it is required to be a shell builtin.
This command can be useful where part of a script can execute in parallel to implement a barrier where an upcoming section depends on the successful completion of the preceding sections.
The following example will fetch the src/ directory from a machine named iona using rsync and simultaneously update the libraries on which this program depends, before building the combination.
Wait for specified job control id number: