Toolbox Aid

August 9th, 2024 2:00 PM Mr. Q Categories: Command

Command: watch

The watch command is used to execute a command repeatedly at specified intervals and display the output. This is useful for monitoring changes in command output or system status in real-time.

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Commands and Outputs:

• Command: watch command Description: Execute the specified command repeatedly and display the output, updating every 2 seconds by default. Sample Command and Output:

  $ watch df -h

Output:

  Every 2s: df -h                                           <date and time>

  Filesystem      Size  Used Avail Use% Mounted on
  /dev/sda1       50G   20G   28G  43% /
  tmpfs            2.0G  1.0M  2.0G   1% /run
  /dev/sdb1       100G   40G   55G  42% /data

• Command: watch -n seconds command Description: Execute the specified command every seconds instead of the default 2-second interval. Sample Command and Output:

  $ watch -n 5 'ls -l /var/log'

Output:

  Every 5s: ls -l /var/log                             <date and time>

  total 1024
  -rw-r--r-- 1 root root   1234 Aug  9 10:00 syslog
  -rw-r--r-- 1 root root   5678 Aug  9 11:00 kern.log
  -rw-r--r-- 1 root root   9101 Aug  9 12:00 auth.log

• Command: watch -d command Description: Highlight changes between updates. The -d flag makes the differences between updates visible. Sample Command and Output:

  $ watch -d df -h

Output:

  Every 2s: df -h                                           <date and time>

  Filesystem      Size  Used Avail Use% Mounted on
  /dev/sda1       50G   20G   28G  43% /
  tmpfs            2.0G  1.0M  2.0G   1% /run
  /dev/sdb1       100G   40G   55G  42% /data

Changes will be highlighted to show differences from the previous output.

Note: Use quotes around the command if it contains spaces or special characters.