If invoked with no arguments, the
wait utility waits until all existing child processes in the background have terminated.
Available operands:
pid
If a
pid operand is specified, and it is the process ID of a background child process that still exists, the
wait utility waits until that process has completed and consumes its status information, without consuming the status information of any other process.
If a pid operand is specified that is not the process ID of a child background process that still exists,
wait exits without waiting for any processes to complete.
The
wait utility exits with one of the following values:
0
The wait utility was invoked with no operands and all of the existing background child processes have terminated, or the process specified by the pid operand exited normally with 0 as its exit status.
>0
The specified process did not exist and its exit status information was not available, or the specified process existed or its exit status information was available, and it terminated with a non-zero exit status.
If the specified process terminated abnormally due to the receipt of a signal, the exit status information of
wait contains that termination status as well.