watch

Have you ever wanted to run some command periodically, usually to wait for some change in the result (like waiting for some ACL to be propagated, a price value to change, etc)?

Seek no more! Do you know the "watch" unix command?

watch -n 60 <command>

This will run <command> every 60 seconds! And you can inspect the output every time it does.

Its usage is quite simple. The help output is:

Usage:

 watch [options] command

Options:

  -b, --beep             beep if command has a non-zero exit

  -c, --color            interpret ANSI color and style sequences

  -d, --differences[=<permanent>]

                         highlight changes between updates

  -e, --errexit          exit if command has a non-zero exit

  -g, --chgexit          exit when output from command changes

  -n, --interval <secs>  seconds to wait between updates

  -p, --precise          attempt run command in precise intervals

  -t, --no-title         turn off header

  -x, --exec             pass command to exec instead of "sh -c"

 -h, --help     display this help and exit

 -v, --version  output version information and exit

Useful command to know!