| .TH WATCH 1 "1999 Apr 3" " " "Linux User's Manual" |
| .SH NAME |
| watch \- execute a program periodically, showing output fullscreen |
| .SH SYNOPSIS |
| .B watch |
| .I [\-dhvt] [\-n <seconds>] [\-\-differences[=cumulative]] [\-\-help] [\-\-interval=<seconds>] [\-\-no\-title] [\-\-version] <command> |
| .SH DESCRIPTION |
| .BR watch |
| runs |
| .I command |
| repeatedly, displaying its output (the first screenfull). This allows you to |
| watch the program output change over time. By default, the program is run |
| every 2 seconds; use |
| .I -n |
| or |
| .I --interval |
| to specify a different interval. |
| .PP |
| The |
| .I -d |
| or |
| .I --differences |
| flag will highlight the differences between successive updates. The |
| .I --cumulative |
| option makes highlighting "sticky", presenting a running display of all |
| positions that have ever changed. The |
| .I -t |
| or |
| .I --no-title |
| option turns off the header showing the interval, command, and current |
| time at the top of the display, as well as the following blank line. |
| .PP |
| .BR watch |
| will run until interrupted. |
| .SH NOTE |
| Note that |
| .I command |
| is given to "sh -c" |
| which means that you may need to use extra quoting to get the desired effect. |
| .PP |
| Note that POSIX option processing is used (i.e., option processing stops at |
| the first non-option argument). This means that flags after |
| .I command |
| don't get interpreted by |
| .BR watch |
| itself. |
| .SH EXAMPLES |
| .PP |
| To watch for mail, you might do |
| .IP |
| watch \-n 60 from |
| .PP |
| To watch the contents of a directory change, you could use |
| .IP |
| watch \-d ls \-l |
| .PP |
| If you're only interested in files owned by user joe, you might use |
| .IP |
| watch \-d 'ls \-l | fgrep joe' |
| .PP |
| To see the effects of quoting, try these out |
| .IP |
| watch echo $$ |
| .IP |
| watch echo '$$' |
| .IP |
| watch echo "'"'$$'"'" |
| .PP |
| You can watch for your administrator to install the latest kernel with |
| .IP |
| watch uname -r |
| .PP |
| (Just kidding.) |
| .SH BUGS |
| Upon terminal resize, the screen will not be correctly repainted until the |
| next scheduled update. All |
| .I --differences |
| highlighting is lost on that update as well. |
| .PP |
| Non-printing characters are stripped from program output. Use "cat -v" as |
| part of the command pipeline if you want to see them. |
| .SH AUTHORS |
| The original |
| .B 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. |