65
15
From man watch
:
Non-printing characters are stripped from program output. Use "cat -v" as part of the command pipeline if you want to see them.
So how do I use cat -v
if I want to see the colored output from:
watch ls -al --color
65
15
From man watch
:
Non-printing characters are stripped from program output. Use "cat -v" as part of the command pipeline if you want to see them.
So how do I use cat -v
if I want to see the colored output from:
watch ls -al --color
74
The right command is
watch --color "ls -a1 --color"
It isn't documented in the man page or the --help screen. I has to use strings to find it.
27
I think it may not be possible with the 'watch' command. Here is a longer way of doing it:
while true; do clear; date;echo;ls -al --color; sleep 2; done
You could put this in a script, for example:
echo "while true; do clear; date;echo;\$*;sleep 2; done" > watch2
chmod +x watch2
./watch2 ls -al --color
To clarify, here's why I think it's not possible with the 'watch' command. See what happens if you use cat -v:
watch "ls -al --color|cat -v"
It shows you the color control characters...which I think is not what you want.
man watch
clearly suggests that it should be possible without dissing watch
. – Paweł Gościcki – 2010-03-29T19:27:46.650
It doesn't say you will be able to see colors. It says you will be able to see the non-printable characters. Try my command as above with cat -v
to see what man watch
was talking about. – davr – 2010-03-29T20:03:53.460
OK. It seems I must accept the fact that it's simply impossible. – Paweł Gościcki – 2010-03-31T15:37:57.553
Is there a way to suppress the blinking that results from the cycles of clear and print operations, a behavior not present in the watch
command? – user001 – 2016-10-01T02:43:39.300
1You can reduce the duration of the blink a little by a) collecting the data to be displayed into a variable, b) clearing the screen, c) printing the variable. – Nick Russo – 2016-12-13T18:21:59.780
1@NickRusso thanks for the suggestion. Something like this greatly reduces the flickering: while true; do out=$(date;echo;ls -al --color);clear;echo $out;sleep 2;done
– Kevin Mark – 2017-07-23T14:21:57.383
Also consider trimming line length to fit in terminal: https://superuser.com/a/58812/114579
– nobar – 2017-09-15T21:18:26.3271
@KevinMark: You should use quotes to handle multiple lines: echo "$out"
. https://stackoverflow.com/q/2414150/86967
@nobar You're right. Looks like it needs quotes in bash not not zsh. – Kevin Mark – 2017-09-15T21:27:04.283
@KevinMark You can put the "clear" command inside the parentheses. It just prints a terminal control code. See also my longer answer https://superuser.com/a/1270584/21952.
– user21952-is-a-great-name – 2017-11-21T20:57:43.2536
If you're using a Mac, like me, watch
from Homebrew does not support colour.
What you want is fswatch but it's not Homebrew yet. To install it you'll want to do the slightly more convoluted
https://raw.github.com/mlevin2/homebrew/116b43eaef08d89054c2f43579113b37b4a2abd3/Library/Formula/fswatch.rb
See this SO answer for usage.
fswatch is available on Homebrew 0.9.5 – code_monk – 2014-10-20T01:45:09.290
2This only works for the filesystem, while watch
applies to a command – Brice – 2014-01-07T15:49:49.287
1
UPDATE: Turns out the latest versions of watch
fixed the problem. So, if the colors of watch --color
are wrong, it's probably better to just update it (on my system, it's in the procps
package).
The color support in watch --color
is limited in my experience (though sufficient for ls -l --color
). Here's my version of @davr's answer with some extra features, most importantly reduced flicker. You can put it in your .bashrc and use it as cwatch ls -l --color
.
# `refresh cmd` executes clears the terminal and prints
# the output of `cmd` in it.
function refresh {
tput clear || exit 2; # Clear screen. Almost same as echo -en '\033[2J';
bash -ic "$@";
}
# Like watch, but with color
function cwatch {
while true; do
CMD="$@";
# Cache output to prevent flicker. Assigning to variable
# also removes trailing newline.
output=`refresh "$CMD"`;
# Exit if ^C was pressed while command was executing or there was an error.
exitcode=$?; [ $exitcode -ne 0 ] && exit $exitcode
printf '%s' "$output"; # Almost the same as echo $output
sleep 1;
done;
}
You can also try things like
cwatch 'ls -l --color | head -n `tput lines`'
if your terminal has fewer lines than the output. That only works if all the lines are shorter than the terminal width, though. The best workaround I know for that is:
cwatch 'let lines=`tput lines`-2; ls -l --color | head -n $lines'
How do you update your watch version? – Adam Hunyadi – 2017-05-19T20:47:16.327
@PawełGościcki Nevermind, already found it on gitorious, although, couldn't get it to work with phpunit. – Ikke – 2012-01-19T13:11:32.893
1My watch is v0.3.0 and I'm on Ubuntu 10.0 – Paweł Gościcki – 2012-01-19T14:00:06.800
2I've also version 0.3.0 and for simple "ls --color" the watch command will work but for some reason more complex scenarios do not:
watch --color "sudo iwlist wlan0 scanning | egrep 'Quality|ESSID' | egrep --color -i 'foobar|$'"
will eat the colors :( – math – 2012-03-07T13:39:57.690@math: Try swapping your single and double quotes. – Paused until further notice. – 2012-04-11T11:03:03.687
The
watch
from procps (the default on most Linux distros, I believe) has a--color
option since V3.3.2. – sleske – 2013-09-04T22:43:24.727Note that the version 3.3.2 is only available in procps-ng, original procps.sf.net seems development has stopped years ago (version is still 3.2.8 and watch version 0.2.0). Also note to OSX/Darwin users the new and maintained fork of procps-ng doesn't yet compile on OSX using LLVM (see https://github.com/Homebrew/homebrew/pull/20845).
– Brice – 2014-01-07T16:07:44.863