Mastering Linux’s watch Command: Real‑Time Monitoring Made Easy

Linux provides the watch command for repeatedly executing a program and displaying its output in full‑screen mode, which is useful for monitoring changing information without writing custom loops.

Basic usage is simply: watch COMMAND By default, watch runs the specified COMMAND every two seconds and shows the result along with a header line indicating the interval, hostname, and timestamp.

To change the execution interval, use the -n INTERVAL option (seconds). For example, to run date every five seconds: watch -n 5 date The -d (or --differences) flag highlights differences between successive outputs, making it easy to spot changes: watch -d -n 1 date If you want the loop to stop as soon as the command’s output changes, use the -g (or --chgexit) option: watch -g free By default, watch ignores the command’s exit status. You can make it react to non‑zero exit codes by enabling a beep with -b or forcing an exit with -e (or --errexit): watch -e wrong_commands Finally, to hide the header line that shows the interval and timestamp, use the -t (or --no-title) option: watch -t date These options together allow flexible, real‑time monitoring of command output directly from the terminal.