wait 命令

常用示例

说明

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

参数

-n

Wait for any single job from the specified list (or all background jobs if none listed) to complete, and return its exit status. Available since Bash 4.3.

-f

Force wait for each process to actually terminate before returning, rather than returning when the job status changes (e.g., when stopped). Requires job control to be enabled.

-p _varname_

Assign the PID or job ID of the completed job to the variable _varname_. Most useful with -n to identify which job finished. Available since Bash 5.1.