watch(1) - phpMan

WATCH(1)                               Linux User's Manual                               WATCH(1)



NAME
       watch - execute a program periodically, showing output fullscreen

SYNOPSIS
       watch [-bdehpvtx] [-n seconds] [--beep] [--differences[=cumulative]] [--errexit] [--exec]
       [--help] [--interval=seconds] [--no-title] [--precise] [--version] 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; use -n or --interval to specify a different interval. Normally, this
       interval is interpreted as the amout of time between the completion of one run of command
       and the beginning of the next run. However, with the -p or --precise option, you can 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 con-
       tinuously increase.

       The -d or --differences flag will highlight the differences between successive updates.
       The --cumulative option makes highlighting "sticky", presenting a running display of all
       positions that have ever changed.  The -t or --no-title option turns off the header show-
       ing the interval, command, and current time at the top of the display, as well as the fol-
       lowing blank line.  The -b or --beep option causes the command to beep if it has a non-
       zero exit.

       watch will normally run until interrupted. If you want watch to exit on an error from the
       program running use the -e or --errexit options, which will cause watch to exit if the
       return value from the program is non-zero.


NOTE
       Note that command is given to "sh -c" which means that you may need to use extra quoting
       to get the desired effect.  You can disable this with the -x or --exec option, which
       passes the command to exec(2) instead.

       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.

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

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



                                            2008 Jan 8                                   WATCH(1)

Generated by $Id: phpMan.php,v 4.49 2006/02/26 13:18:18 chedong Exp $ Author: Che Dong
On Apache
Under GNU General Public License
2012-05-26 04:52 @38.107.179.236 Crawled by CCBot/1.0 (+http://www.commoncrawl.org/bot.html)