watch [man page] - execute a program periodically, showing output fullscreen

2. Synopsis

watch [-dhvt] [-n seconds] [--differences[=cumulative]]
      [--help] [--interval=seconds] [--no-title]
      [--version] command 

3. Frequently used options

-n seconds interval in seconds 

4. Examples

Watch is utility which helps you to WATCH for changes. For example if we want to watch content of directory for new files we can do:

$ watch ls ~/ 

By default watch update screen every 2 seconds. To change this interval we can use -n option. If we want to watch to refresh screen every 0.5 second we do:

watch -n 0.5 ls ~/