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
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.
watch --color "sudo iwlist wlan0 scanning | egrep 'Quality|ESSID' | egrep --color -i 'foobar|$'"
will eat the colors :(
watch --version
=> watch from procps-ng 3.3.16
). watch --help
=> -c, --color interpret ANSI color and style sequences
. Guessing they must have updated the documentation in newer versions.
Apr 24, 2020 at 17:18
I think it may not be possible with the 'watch' command. Here is a longer way of doing it:
while true; do clear; date;echo;ls -al --color; sleep 2; done
You could put this in a script, for example:
echo "while true; do clear; date;echo;\$*;sleep 2; done" > watch2
chmod +x watch2
./watch2 ls -al --color
To clarify, here's why I think it's not possible with the 'watch' command. See what happens if you use cat -v:
watch "ls -al --color|cat -v"
It shows you the color control characters...which I think is not what you want.
man watch
clearly suggests that it should be possible without dissing watch
.
Mar 29, 2010 at 19:27
cat -v
to see what man watch
was talking about.
while true; do out=$(date;echo;ls -al --color);clear;echo $out;sleep 2;done
Jul 23, 2017 at 14:21
echo "$out"
. stackoverflow.com/q/2414150/86967
Sep 15, 2017 at 21:20
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.
--color
flag mentioned in this answer. watch --version
=> watch from procps-ng 3.3.16
.
Apr 24, 2020 at 17:22
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'