WATCH(1)							   User Commands							  WATCH(1)

NAME

       watch - execute a program periodically, showing output fullscreen

SYNOPSIS

       watch [options] command

DESCRIPTION

       watch runs command repeatedly, displaying its output and errors (the first screenfull).	This allows you to watch the program output change
       over time.  By default, the program is run every 2 seconds.  By default, watch will run until interrupted.

OPTIONS

       -d, --differences [permanent]
	      Highlight the differences between successive updates.  Option will read optional argument that changes highlight	to  be	permanent,
	      allowing to see what has changed at least once since first iteration.

       -n, --interval seconds
	      Specify update interval.	The command will not allow quicker than 0.1 second interval, in which the smaller values are converted.

       -p, --precise
	      Make  watch  attempt to run command every interval seconds. Try it with ntptime and notice how the fractional seconds stays (nearly)
	      the same, as opposed to normal mode where they continuously increase.

       -t, --no-title
	      Turn off the header showing the interval, command, and current time at the top of the display, as well as the following blank line.

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

       -e, --errexit
	      Freeze updates on command error, and exit after a key press.

       -g, --chgexit
	      Exit when the output of command changes.

       -c, --color
	      Interpret ANSI color sequences.

       -x, --exec
	      command is given to sh -c which means that you may need to use extra quoting to get  the	desired  effect.   This  with  the  --exec
	      option, which passes the command to exec(2) instead.

       -h, --help
	      Display help text and exit.

       -v, --version
	      Display version information and exit.

NOTE

       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.

EXAMPLES

       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 "'"'$$'"'"

       To see the effect of precision time keeping, try adding -p to

	      watch -n 10 sleep 1

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

	      watch uname -r

       (Note that -p isn't guaranteed to work across reboots, especially in the face of ntpdate or other bootup time-changing mechanisms)

BUGS

       Upon terminal resize, the screen will not be correctly repainted until the next scheduled update.  All --differences 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.

       Combining  Characters  that are supposed to display on the character at the last column on the screen may display one column early, or they
       may not display at all.

       Combining Characters never count as different in --differences mode.  Only the base character counts.

       Blank lines directly after a line which ends in the last column do not display.

       --precise mode doesn't yet have advanced temporal distortion technology to compensate for a command that takes more than  interval  seconds
       to  execute.  watch also can get into a state where it rapid-fires as many executions of command as it can to catch up from a previous exe-
       cutions running longer than interval (for example, netstat taking ages on a DNS lookup).

EXIT STATUS

	      0      Success.
	      1      Various failures.
	      2      Forking the process to watch failed.
	      3      Replacing child process stdout with write side pipe failed.
	      4      Command execution failed.
	      5      Closign child process write pipe failed.
	      7      IPC pipe creation failed.
	      8      Getting child process return value with waitpid(2) failed, or command exited up on error.
	      other  The watch will propagate command exit status as child exit status.
AUTHORS

       The original watch was written by Tony Rems <rembo@unisoft.com> in 1991, with mods and corrections by Francois Pinard.  It was reworked and
       new  features  added  by  Mike Coleman <mkc@acm.org> in 1999. The beep, exec, and error handling features were added by Morty Abzug <morty@
       frakir.org> in 2008.  On a not so dark and stormy morning in March of 2003,  Anthony  DeRobertis  <asd@suespammers.org>	got  sick  of  his
       watches	that  should update every minute eventually updating many seconds after the minute started, and added microsecond precision.  Uni-
       code support was added in 2009 by Jarrod Lowe <procps@rrod.net>

procps-ng							     June 2011								  WATCH(1)