Manual: watch

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

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

       -c, --color
	      Interpret ANSI color and style sequences.

       -C, --no-color
	      Do not interpret ANSI color and style sequences.

       -d, --differences[=permanent]
	      Highlight	 the  differences  between successive updates. If the optional permanent argument is
	      specified then watch will show all changes since the first iteration.

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

       -g, --chgexit
	      Exit when the visible output of command changes. Changes that are off the screen due to  small
	      screen size or large output will not cause watch to exit.

       -n, --interval seconds
	      Specify  update  interval.   The	command	 will not allow quicker than 0.1 second interval, in
	      which the smaller values are converted. Both '.' and ',' work for any locales.  The  WATCH_IN‐
	      TERVAL  environment can be used to persistently set a non-default interval (following the same
	      rules and formatting).

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

       -q, --equexit 
	      Exit when output of command does not change for the given number of cycles.

       -r, --no-rerun
	      Do  not  run  the	 program on terminal resize, the output of the program will re-appear at the
	      next regular run time.

       -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.

       -w, --no-wrap
	      Turn off line wrapping. Long lines will be truncated instead of wrapped to the next line.

       -x, --exec
	      Pass command to exec(2) instead of sh -c which reduces the need to use extra  quoting  to	 get
	      the desired effect.

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

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

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	     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 er‐
		     ror.
	      other  The watch will propagate command exit status as child exit status.
ENVIRONMENT
       The behavior of watch is affected by the following environment variables.

       WATCH_INTERVAL
	      Update interval, follows the same rules as the --interval command line option.

NOTES
       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.

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. When using the --no-rerun	 option,  no
       output of will be visible.

       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(8) taking ages on a DNS lookup).

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 (if present)
       or other bootup time-changing mechanisms)

REPORTING BUGS
       Please send bug reports to procps@freelists.org

procps-ng					 2024-07-19					    WATCH(1)