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Execute a program periodically, showing output full screen

      watch [-dhv] [-n  ]  [--differences[=cumulative]]
       [--help] [--interval=] [--version] 

       watch  runs command repeatedly, displaying its output (the
       first screenfull).  This allows you to watch  the  program
       output  change  over time.  By default, the program is run
       every 2 seconds; use -n or --interval to specify a differ­
       ent interval.

       The  -d  or  --differences flag will highlight the differ­
       ences between successive updates.  The --cumulative option
       makes  highlighting "sticky", presenting a running display
       of all positions that have ever changed.

       watch will run until interrupted.

       Note that command is given to "sh -c" which means that you
       may need to use extra quoting to get the desired effect.

       Note  that  POSIX  option processing is used (i.e., option
       processing stops at the first non-option argument).   This
       means  that  flags  after command don't get interpreted by
       watch itself.

       To watch for mail, you might do

              watch -n 60 from

       To watch the contents of a directory change, you could use

              watch -d ls -l

       If  you're only interested in files owned by user joe, you
       might use

              watch -d 'ls -l | fgrep joe'

       To see the effects of quoting, try these out

              watch echo $$

              watch echo '$$'

              watch echo "'"'$$'"'"

       You can watch for your administrator to install the latest
       kernel with

              watch uname -r

       (Just kidding.)

       Upon  terminal  resize,  the  screen will not be correctly
       repainted until the next scheduled update.  All  --differ­
       ences highlighting is lost on that update as well.

       Non-printing  characters are stripped from program output.
       Use "cat -v" as part of the command pipeline if  you  want
       to see them.

"Advertising may be described as the science of arresting the human intelligence long enough to get money from it." - Stephen Leacock

Related commands:

builtin - Run a shell builtin
crontab - Schedule a command to run at a later time
chroot - Run a command with a different root directory
exec - Execute a command
if - Conditionally perform a command
nohup - Run a command immune to hangups
su - Run a command with substitute user and group id
watch - Execute/display a program periodically
.period - Run commands from a file