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WATCH(1)			 User Commands			      WATCH(1)

       watch - execute a program periodically, showing output fullscreen

       watch [options] command

       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, command is run	every 2	seconds	and watch will
       run until interrupted.

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

       -n, --interval seconds
	      Specify  update  interval.   The	command	will not allow quicker
	      than 0.1 second interval,	in which the smaller values  are  con-
	      verted. Both '.' and ',' work for	any locales.

       -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 continu-
	      ously 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

       -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 and style 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.

	      0	     Success.
	      1	     Various failures.
	      2	     Forking the process to watch failed.
	      3	     Replacing child  process  stdout  with  write  side  pipe
	      4	     Command execution failed.
	      5	     Closing 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.
       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.
       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

       --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 executions
       running longer than interval (for example, netstat taking ages on a DNS
       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)

procps-ng			  2016-06-03			      WATCH(1)


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