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
          permanent, 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
          converted. 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
          continuously 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)


Personal Opportunity - Free software gives you access to billions of dollars of software at no cost. Use this software for your business, personal use or to develop a profitable skill. Access to source code provides access to a level of capabilities/information that companies protect though copyrights. Open source is a core component of the Internet and it is available to you. Leverage the billions of dollars in resources and capabilities to build a career, establish a business or change the world. The potential is endless for those who understand the opportunity.

Business Opportunity - Goldman Sachs, IBM and countless large corporations are leveraging open source to reduce costs, develop products and increase their bottom lines. Learn what these companies know about open source and how open source can give you the advantage.

Free Software

Free Software provides computer programs and capabilities at no cost but more importantly, it provides the freedom to run, edit, contribute to, and share the software. The importance of free software is a matter of access, not price. Software at no cost is a benefit but ownership rights to the software and source code is far more significant.

Free Office Software - The Libre Office suite provides top desktop productivity tools for free. This includes, a word processor, spreadsheet, presentation engine, drawing and flowcharting, database and math applications. Libre Office is available for Linux or Windows.

Free Books

The Free Books Library is a collection of thousands of the most popular public domain books in an online readable format. The collection includes great classical literature and more recent works where the U.S. copyright has expired. These books are yours to read and use without restrictions.

Source Code - Want to change a program or know how it works? Open Source provides the source code for its programs so that anyone can use, modify or learn how to write those programs themselves. Visit the GNU source code repositories to download the source.


Study at Harvard, Stanford or MIT - Open edX provides free online courses from Harvard, MIT, Columbia, UC Berkeley and other top Universities. Hundreds of courses for almost all major subjects and course levels. Open edx also offers some paid courses and selected certifications.

Linux Manual Pages - A man or manual page is a form of software documentation found on Linux/Unix operating systems. Topics covered include computer programs (including library and system calls), formal standards and conventions, and even abstract concepts.