wait

Wait for all background jobs to complete

$ wait

$ wait [pid]

$ wait [pid1] [pid2]

$ wait %1

$ command & wait $!; echo "Exit status: $?"

wait [pid|jobspec...]

wait is a shell builtin that pauses execution until specified background processes complete. It returns the exit status of the waited-for process.
When given a PID, wait blocks until that process terminates. With a job specification (%1, %2, etc.), it waits for that specific job. Without arguments, it waits for all child processes.
This is essential for scripts that spawn background processes and need to synchronize their completion or check their exit status.
The special variable $! contains the PID of the last background process, commonly used with wait: command & pid=$!; wait $pid

pid

Process ID to wait for

Job specification (e.g., %1, %+, %-)

Wait only works with child processes of the current shell. You cannot wait for arbitrary processes started by other shells or users.
In bash, wait -n (wait for any single job) is useful for processing results as jobs complete, but this option isn't available in all shells.
Exit status is only available immediately after wait returns. Calling wait again on the same PID may return different results.

jobs(1), bg(1), fg(1), kill(1), bash(1)