flock Command: Lock Files in Shell

In the shell, the flock command can be used to lock files. It allows exclusive locking of files or directories to prevent other processes from performing read and write operations at the same time.

flock -x file.lock your_command

The file.lock is a file used to store locking information, and your_command is the command to be executed. When running the flock command, it will attempt to acquire an exclusive lock on the file.lock file. If successful, it will execute the your_command. If it fails to acquire the lock, it will wait until it can acquire it.

Additionally, the ‘flock’ command can be used to lock critical sections in the script, ensuring that only one process can execute the key parts of the script at the same time.

(
    flock -x 200

    # Critical section

) 200>/var/lock/mylockfile

In this example, the code block within parentheses represents the critical section, where flock -x 200 will acquire an exclusive lock on the file descriptor 200. This ensures that only one process can execute the code within the critical section at the same time.