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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 perma‐
	      nent, 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  con‐
	      verted.

       -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
	      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 executions
       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.  Unicode support
       was added in 2009 by Jarrod Lowe ⟨procps@rrod.net⟩

procps-ng			   June 2011			      WATCH(1)
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