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_INTERVAL 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	 ef‐
	      fect.

       -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 error.
	      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	com‐
       mand  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)