watchcommand is a system utility able to execute a command every n seconds by clearing the screen and displaying the output of the command each time the interval is over. This command is very simple to use and very effective: it can be used to check the size in bytes of a file while downloading it, or it can be used on Linux to jiggle around the mouse every ~5 minutes with the command
xdotoolin order to keep the computer awake.
watchhas a very simple syntax: the amount in seconds to wait between executions is specified in seconds using the
-nflag and the default value is 2. Also, differences between older and newer outputs are highlighted if the
-dflag is used. Example: Watch the size of "ubuntu.iso" every 5 seconds
watch -n 5 du -h ubuntu.isoExample: Watch the contents of "site.html" every 2 seconds and highlight the differencies between iterations
watch -d cat site.html