wait Command
Intermediate Shell Scripting man(1)Wait for background processes to finish
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📅 Updated: Apr 29, 2026
SYNTAX
wait [PID]...
What Does wait Do?
wait pauses the shell until specified background processes complete. Without arguments, it waits for all background jobs. With a PID or job ID, it waits for that specific process.
wait returns the exit status of the waited-for process, making it essential for parallel processing scripts that need to check if background tasks succeeded or failed.
wait is commonly used with background (&) processes, parallel command execution, and coordinating multiple asynchronous operations in shell scripts.
wait returns the exit status of the waited-for process, making it essential for parallel processing scripts that need to check if background tasks succeeded or failed.
wait is commonly used with background (&) processes, parallel command execution, and coordinating multiple asynchronous operations in shell scripts.
Options & Flags
| Option | Description | Example |
|---|---|---|
| PID | Wait for specific process | wait 1234 |
| %N | Wait for job number N | wait %1 |
| -n | Wait for any single job to complete (bash 4.3+) | wait -n |
| -p VAR | Store the PID that completed (bash 5.1+) | wait -n -p completed_pid |
| (no args) | Wait for all background jobs | wait |
Practical Examples
#1 Wait for all background jobs
Runs 3 commands in parallel and waits for all to finish.
$ cmd1 & cmd2 & cmd3 & wait; echo "All done"#2 Wait for specific process
Starts a task, captures its PID, waits for it, and checks its exit status.
$ long_task & PID=$!; echo "Started $PID"; wait $PID; echo "Exit code: $?"#3 Parallel with error checking
Runs tasks in parallel and checks each exit code independently.
$ task1 & P1=$!; task2 & P2=$!; wait $P1 || echo "task1 failed"; wait $P2 || echo "task2 failed"#4 Wait for any job
Starts multiple jobs and continues as soon as any one finishes.
$ for i in 1 2 3 4 5; do slow_task $i & done; wait -n; echo "First one done"#5 Parallel file processing
Processes all CSV files in parallel, then continues.
$ for f in *.csv; do process "$f" & done; wait; echo "All files processed"Tips & Best Practices
$! captures last background PID: After command &, $! contains its PID. Save it immediately: cmd & PID=$! for use with wait later.
Exit code propagation: wait returns the exit code of the process it waited for. Use $? after wait to check if the background task succeeded.
Only waits for children: wait can only wait for processes started by the current shell. It cannot wait for arbitrary PIDs from other sessions.
Frequently Asked Questions
How do I wait for background processes?
Use wait with no arguments to wait for all background jobs, or wait PID for a specific process.
How do I get the exit code of a background process?
cmd & PID=$!; wait $PID; echo $?. The $? after wait gives the exit code of the background process.
How do I run commands in parallel and wait?
Start each with &, then call wait: cmd1 & cmd2 & cmd3 & wait. This waits for all three to complete.
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