39a2f5d717
A patch from Debian. Bug-Debian: http://bugs.debian.org/129334 Backported-by: Sami Kerola <kerolasa@iki.fi>
125 lines
3.1 KiB
Groff
125 lines
3.1 KiB
Groff
.TH WATCH 1 "2010 Mar 01" " " "Linux User's Manual"
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.SH NAME
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watch \- execute a program periodically, showing output fullscreen
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.SH SYNOPSIS
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.na
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.B watch
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.RB [ \-bdehvtx ]
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.RB [ \-n
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.IR seconds ]
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.RB [ \-\-beep ]
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.RB [ \-\-color ]
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.RB [ \-\-differences[=\fIcumulative\fP]]
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.RB [ \-\-errexit ]
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.RB [ \-\-exec ]
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.RB [ \-\-help ]
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.RB [ \-\-interval=\fIseconds\fP]
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.RB [ \-\-no\-title ]
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.RB [ \-\-version ]
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.I command
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.SH DESCRIPTION
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.B watch
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runs
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.I command
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repeatedly, displaying its output and errors (the first screenfull). This
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allows you to
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watch the program output change over time. By default, the program is run
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every 2 seconds; use
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.B \-n
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or
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.B \-\-interval
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to specify a different interval.
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.PP
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The
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.B \-d
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or
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.B \-\-differences
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flag will highlight the differences between successive updates. Using
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.B \-\-differences=\fIcumulative\fP
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makes highlighting "sticky", presenting a running display of all
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positions that have ever changed. The
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.B \-t
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or
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.B \-\-no\-title
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option turns off the header showing the interval, command, and current
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time at the top of the display, as well as the following blank line. The
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.I \-b
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or
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.I \-\-beep
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option causes the command to beep if it has a non-zero exit.
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.PP
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.B watch
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will normally run until interrupted. If you want
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.B watch
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to exit on an error from the program running use the
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.I \-e
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or
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.I \-\-errexit
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options, which will cause
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.B watch
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to exit if the return value from the program is non-zero.
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.PP
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By default \fBwatch\fR will normally not pass escape characters, however
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if you use the \fI\-\-c\fR or \fI\-\-color\fR option, then
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\fBwatch\fR will interpret ANSI color sequences for the foreground.
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.SH NOTE
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Note that
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.I command
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is given to "sh \-c"
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which means that you may need to use extra quoting to get the desired effect.
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You can disable this with the
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.I -x
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or
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.I --exec
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option, which passes the command to exec(2) instead.
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.PP
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Note that POSIX option processing is used (i.e., option processing stops at
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the first non\-option argument). This means that flags after
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.I command
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don't get interpreted by
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.BR watch
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itself.
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.SH EXAMPLES
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.PP
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To watch for mail, you might do
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.IP
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watch \-n 60 from
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.PP
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To watch the contents of a directory change, you could use
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.IP
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watch \-d ls \-l
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.PP
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If you're only interested in files owned by user joe, you might use
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.IP
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watch \-d 'ls \-l | fgrep joe'
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.PP
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To see the effects of quoting, try these out
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.IP
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watch echo $$
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.br
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watch echo '$$'
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.br
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watch echo "'"'$$'"'"
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.PP
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You can watch for your administrator to install the latest kernel with
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.IP
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watch uname \-r
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.PP
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(Just kidding.)
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.SH BUGS
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Upon terminal resize, the screen will not be correctly repainted until the
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next scheduled update. All
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.B \-\-differences
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highlighting is lost on that update as well.
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.PP
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Non-printing characters are stripped from program output. Use "cat -v" as
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part of the command pipeline if you want to see them.
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.SH AUTHORS
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The original
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.B watch
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was written by Tony Rems <rembo@unisoft.com> in 1991, with mods and
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corrections by Francois Pinard. It was reworked and new features added by
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Mike Coleman <mkc@acm.org> in 1999. The beep, exec, and error handling
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features were added by Morty Abzug <morty@frakir.org> in 2008.
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