Linux Command: watch

watch executes a command repeatedly at a specified interval, displaying the output full-screen. It is perfect for monitoring changes in real time — disk usage, network connections, process lists, and any command output. watch clears the screen and re-runs the command, showing the current time, interval, and command at the top. With -d, it highlights differences between updates. watch is one of the simplest yet most useful monitoring tools. It turns any command into a real-time dashboard.

Syntax

watch [OPTION]... COMMAND

Key Options

• -n N — Update every N seconds (default 2)
• -d — Highlight differences between updates
• -t — Hide the header
• -g — Exit when output changes
• -e — Exit on error

Examples

Monitor disk space

watch -n 10 df -h

Monitor connections

watch -n 1 "ss -s"

Highlight changes

watch -d "ls -la /var/log/"

Pro Tips

• Use quotes for pipes: watch "command | grep filter". Without quotes, the pipe is interpreted by the current shell.
• -d highlights what changed between refreshes. Very useful for spotting changes in large outputs.
• Commands using colors or terminal features may display poorly. Use --color flag or pipe through col -b if needed.

Learn more: Full watch reference →