What is the purpose of the “wait” command in the shell?

In a shell, the wait command is used to wait for one or more processes to complete. Typically, when using background processes in a shell script, the wait command can be used to ensure that all background processes are completed before continuing with the script execution.

The function of the wait command can be summarized as follows:

1. Wait for the designated process to finish. You can use either the process ID or the job ID passed as an argument to a command running in the background.
2. If no process ID or job ID is specified, the wait command will wait for all child processes started by the current shell to complete.
3. When the wait command pauses the current shell execution while waiting for a process to finish, it can be used to ensure that background processes complete before executing subsequent commands.
4. When the wait command waits for a process to finish, it will return the exit status of the last completed process. This exit status can be used to determine if the process completed successfully.

In short, the ‘wait’ command is used in shell scripts to wait for processes to complete, ensuring that all background processes are finished before continuing with the script.