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I'd like to be able to tail the output of a server log file that has messages like:


etc, and if it's SEVERE, show the line in red; if it's INFO, in green. What kind of alias can I setup for a tail command that would help me do this?

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18 Answers 18

up vote 143 down vote accepted

Try out multitail. This is an übergeneralization of tail -f. You can watch multiple files in separate windows, highlight lines based on their content, and more.

multitail -c /path/to/log

The colors are configurable. If the default color scheme doesn't work for you, write your own in the config file. For example, call multitail -cS amir_log /path/to/log with the following ~/.multitailrc:


Another solution, if you're on a server where it's inconvenient to install non-standard tools, is to combine tail -f with sed or awk to add color selection control sequences. This requires tail -f to flush its standard output without delay even when its standard output is a pipe, I don't know if all implementations do this.

tail -f /path/to/log | awk '
  /INFO/ {print "\033[32m" $0 "\033[39m"}
  /SEVERE/ {print "\033[31m" $0 "\033[39m"}


tail -f /path/to/log |
sed -e 's/\(.*INFO.*\)/\o033[32m\1\o033[39m/' \
    -e 's/\(.*SEVERE.*\)/\o033[31m\1\o033[39m/'

If your sed isn't GNU sed, replace \o033 by a literal escape character.

Yet another possibility is to run tail -f in an Emacs shell buffer and use Emacs's syntax coloring abilities.

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how can you do this with sed? (sorry for being lazy and not figuring it out myself!) But would you please add a sed example as well. – Ali Nov 28 '11 at 16:41
@Ali Sed is less convenient because it doesn't have a syntax for the escape character, you need to have it literally in the script or use a shell quoting method to work it in. I recommend that you use awk. – Gilles Nov 28 '11 at 17:18
@Gilles Thank you for sharing your knowledge. Though, is there a way to do this with vim as like Emacs does? – Benjamin Jun 24 '12 at 17:01
@Gilles In your tail -f with awk code, if a string doesn't have INFO and SEVERE, the string isn't be printed. How can I print the remain strings either? (The string doesn't need to be colored) – Benjamin Jun 29 '12 at 10:32
@Benjamin Add ; next before the closing braces to skip further processing, and a new processing line 1 {print} at the end (1 means always). – Gilles Jun 29 '12 at 11:58

grc, the generic colouriser is pretty cool


Just do

grc tail -f /var/log/apache2/error.log

and enjoy

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This is exactly what I needed: lightweight and simple. The coloring isn't exactly right for my log types (custom logs) but any coloring makes it easier for me to follow a log. – rennat Oct 21 '11 at 19:49
For me 'grc' on Debian errors out with: OSError: [Errno 13] Permission denied. Also it depends on Python being installed so it's not relaly lightweight unless you already have it. I have found 'ccze' to work much better, ex. 'tail -f -n 50 /var/log/starbound-server.log | ccze -A'. – Daniel Sokolowski Dec 9 '13 at 3:56
grc default settings in Ubuntu didn't display nice for syslogs or mail.log. It is not easy to understand how to customize it. – lepe Jan 27 '14 at 3:34
I found it quicker and easier way to colorize than multitail. Just did a quick install via source on my CentOS system and upgraded my life. Will install on my other systems too. – zeeshan Jul 12 '14 at 9:51
This looks pretty terrible on nginx logs i.imgur.com/aJbIOfL.png – mpen Sep 3 '14 at 2:34

Have you had a look at ccze? You have the possibility to customize the default colors of some keywords using the option -c or directly in your configuration file. If your screen is clearing after colorizing you must use option -A.


If you really would like to have the complete line colored in red, you could also have a try at the following:

$ tail -f myfile.log | perl -pe 's/.*SEVERE.*/\e[1;31m$&\e[0m/g'

\e[1;31m will give you the red color. If you would like some yellow, use \e[1;33m, and for green use \e[1;32m. The \e[0m restores the normal text color.

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This doesn't work on Mac - I'm upvoting it because it works on Linux. – Amir Afghani Mar 1 '11 at 21:33
Upvoting because while the perl/ansi trick might not, ccze does. – Shadur Nov 13 '11 at 16:02
You can also make your terminal send an alert or "beep" by adding \007 to the end of the regex, like so: perl -pe 's/(ERROR)/\033[31m$1\033[0m\007/g;'. This works awesome if you are using tmux with set -g bell-action any, in which case if you have your log tailing in another window, that window name will alert whenever the regex finds a match. – jonyamo Nov 13 '12 at 4:15
@AmirAfghani This is a linux/unix SE site, therefore I am not sure why you thought it would work on mac. – BЈовић Jun 4 '13 at 6:06
@BЈовић Mac is a Unix. – Chris Down Sep 12 '13 at 19:16

You can use rainbow, which colorizes lines based on regular expressions:

rainbow --red='SEVERE.*' --green='INFO.*' -- tail -f my-file.log

It also comes bundled with predefined configs, for example for Tomcat logs:

rainbow --config=tomcat -- tail -f my-file.log
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Have a look at lnav, the advanced log file viewer.

lnav lnav

It can also pretty print various formats.





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I quite like colorex. Simple, yet satisfying.

tail -f /var/log/syslog | colorex -G '[0-9]{2}:[0-9]{2}:[0-9]{2}' -b $(hostname)
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how is that simple? – Eliran Malka Apr 13 '15 at 10:40

You can use colortail:

colortail -f /var/log/messages
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+1 available at Ubuntu repositories. What I like of colortail compared to ccze is that you can customize freely your patterns using RegEx. Available colors: black, brightblack, white, brightwhite, magenta, brightmagenta, cyan, brightcyan, green,‌​brightgreen, yellow, brightyellow, red,brightred, blue, brightblue. Unfortunately there is no way to set bold or other colors like orange. – lepe Jan 27 '14 at 3:55
I would like to correct one point about my previous comment: "bright"+color includes "bold" (some colors will actually look brighter as well) – lepe Jan 27 '14 at 4:25

Also note that if you just want to look for one matching regex, GNU grep with --color will work — just pipe your tail output through that.

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The OP only wanted to highlight the output, not filter it. Grep won't show non-matching lines... – Coderer Jun 30 '14 at 12:36
If you say grep  -A9999  -B9999 regex, it will show all lines unless you have 10,000 non-matching lines in a row.  Use something like GREP_COLORS="ms=31:sl=33:cx=32" grep -A9999 -B9999 SEVERE to show the word SEVERE in red, the rest of SEVERE lines in yellow, and all other (non-SEVERE) lines (up to 9999) in green. – G-Man Aug 7 '15 at 2:45

To get colored output from standard commands like grep, you should set this alias in your .bashrc

# User specific aliases and functions
alias grep='grep --color=auto'

when you grep something in your file you see something like this, (but probably in red):

[root@linuxbox mydir]# grep "\(INFO\|SEVERE\)" /var/log/logname
this entry is an INFO 
SEVERE this entry is a warn!
this entry is an INFO
this entry is an INFO
SEVERE this entry is a warn!

if want to use tail or awk and want that the color survive to a pipe, then the alias is not enough and you should use the --color=always parameter, for example:

[root@linubox mydir]# grep --color=always "\(INFO\|SEVERE\)" /var/log/logname | tail -f | awk '{ print $1 }'

If you want color text with awk the story is a little bit complex but more powerfull, for example:

[root@linubox mydir]# tail -f /var/log/messages | awk '{if ($5 ~ /INFO/) print "\033[1;32m"$0"\033[0m"; else if ($1 ~ /SEVERE/) print "\033[1;31m"$0"\033[0m"; else print $0}'
this entry is an INFO 
SEVERE this entry is a warn!
this is another ENTRY
this entry is an INFO
this is another ENTRY
this entry is an INFO
SEVERE this entry is a warn!

with each line in its own color.

There are many other way to get colorized text from shell with other tools and they are well descripted by other members.

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Based on @uloBasEI answer, I've tried to use ... | perl ... | perl ..., but Linux pipe gets a bit crazy and is too slow. If I put all rules in only one perl command, it works fine.

For example, create a perl file colorTail.pl as below:

#!/usr/bin/perl -w

while(<STDIN>) {
    my $line = $_;
        s/==>.*<==/\e[1;44m$&\e[0m/gi; #tail multiples files name in blue background
        s/.*exception.*|at .*/\e[0;31m$&\e[0m/gi;  #java errors & stacktraces in red
        s/info.*/\e[1;32m$&\e[0m/gi; #info replacement in green
        s/warning.*/\e[1;33m$&\e[0m/gi; #warning replacement in yellow
    print $line, "\n";

Use it as:

tail -f *.log | perl colorTail.pl
tail -f *.log -f **/*.log | perl colorTail.pl

NOTE: you can use it on MobaXTerm too! Just download perl plug-in from MobaXTerm site.

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tail -f /var/log/logname | source-highlight -f esc -s log
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source-highlight isn't a widely installed command, so you should at least give a link to the project site. – Gilles Mar 16 '11 at 22:45
Available in Fedora 19. – sjas Sep 29 '13 at 14:55
And Ubuntu 12.10. – sjas Sep 29 '13 at 15:10
It looks nice. Its a big package compared to others in this list (26MB). It supports a huge list of languages. It can be customized modifying the config files located at: /usr/share/source-highlight/*.lang (Ubuntu). If you need something simple, go with ccze or colortail. – lepe Jan 27 '14 at 3:46
looks like it depends on boost, which is around 462MB – ecsos May 29 '14 at 21:34

Most of the solutions on this page add the color codes to the logfile as it is generated. That has some problems:

  • If you are later grepping through the log, you'll have to remember to account for the color codes in your grep patterns. (e.g. "grep "ERROR " won't find lines in which the error is highlighted red.)
  • It can only work on the logfiles you are producing yourself, and that you take the trouble to add color codes to.

Instead, this solution adds color as the logfiles is viewed, meaning it can be used on any logfile, no matter where they came from, and they leave the original logfile unmolested, so traditional tools like grep don't get confused by any color codes embedded in the log text.

Better yet, it works for coloring all sorts of text, not just logfiles.

A simple but very flexible tool for coloring ANY terminal text is 'colout'.

pip install colout
myprocess | colout REGEX_WITH_GROUPS color1,color2...

Where any text in the output of 'myprocess' which matches group 1 of the regex will be colored with color1, group 2 with color2, etc.

For example:

tail -f /var/log/mylogfile | colout '^(\w+ \d+ [\d:]+)|(\w+\.py:\d+ .+\(\)): (.+)$' white,black,cyan bold,bold,normal

i.e. the first regex group (parens) matches the initial date in the logfile, the second group matches a python filename, line number and function name, and the third group matches the log message that comes after that. This looks like:

logfile with colored formatting

(This example also uses a sequence of 'bold/normals' as well as the sequence of colors)

Note that lines or parts of lines which don't match any of my regex are still echoed, so this isn't like 'grep --color' - nothing is filtered out of the output.

Obviously this is flexible enough that you can use it with any process, not just tailing logfiles. I usually just whip up a new regex on the fly any time I want to colorize something. For this reason, I prefer colout to any custom logfile-coloring tool, because I only need to learn one tool, regardless of what I'm coloring: logging, test output, syntax highlighting snippets of code in the terminal, etc.

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Shameless plug: I wrote a tool called TxtStyle that does something similar as the options mentioned earlier. You can run it as follows:

tail -f /var/log/syslog | txts --regex '\d+'

You can also define named styles in the config file (~/.txts.conf) and use it like so:

ifconfig | txts --name ifconfig

(ifconfig style is defined out of the box)

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I wrote a bash function that accepts up to three parameters and does a grep-like filter on a text file, and outputs text to the screen in color.

I would also like to see a tail function that would do this, but haven't found one yet.

This function can also be improved - I'd appreciate any help on how to make it better.

function multigrep(){

    #THIS WORKS - Recreate this, using input parameters
    #sed -En '/(App)|(Spe)/p' ./flashlog.txt;

    filename="/Users/stevewarren/Library/Preferences/Macromedia/Flash\ Player/Logs/flashlog.txt";

    for element in "$@"
            #echo $element;


    #CREATE SED EXPRESSION - '/($1)|($2)|(...)/p'

    paramString="sed -En $paramString ./flashlog.txt"

    echo $paramString;
    echo "${txtbld}$(tput setaf 7)" > ./flashlog_output.txt;
    eval $paramString >> ./flashlog_output.txt;
    echo >> ./flashlog_output.txt;
    #cat ./flashlog_output.txt;

    cat ./flashlog_output.txt | while read LINE

        [[  $1 && ${1-x} ]] && 
            if grep -q $1 <<<$LINE; then
                echo "$(tput setaf 3)$LINE"

        [[  $2 && ${2-x} ]] && 
            if grep -q $2 <<<$LINE; then
                echo "$(tput setaf 7)$LINE"

        [[  $3 && ${3-x} ]] && 
            if grep -q $3 <<<$LINE; then
                echo "$(tput setaf 6)$LINE"

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sure !

I wrote long a go a function called "egrepi", based on the 8 color variables definitions. This works ONLY piped like a "tail -f" colored function.

1. setColors

first, the color variables function to be called at first:

setColors ()
set -a
which printf >/dev/null 2>&1 && print=printf || print=print # Mandriva doesn't know about printf

hide='eval tput civis'
show='eval tput cnorm'
CLS=$(tput clear)
bel=$(tput bel)

case ${UNAME} in
# text / foreground
N=$(${print} '\033[1;30m')
n=$(${print} '\033[0;30m')
R=$(${print} '\033[1;31m')
r=$(${print} '\033[0;31m')
G=$(${print} '\033[1;32m')
g=$(${print} '\033[0;32m')
Y=$(${print} '\033[1;33m')
y=$(${print} '\033[0;33m')
B=$(${print} '\033[1;34m')
b=$(${print} '\033[0;34m')
M=$(${print} '\033[1;35m')
m=$(${print} '\033[0;35m')
C=$(${print} '\033[1;36m')
c=$(${print} '\033[0;36m')
W=$(${print} '\033[1;37m')
w=$(${print} '\033[0;37m')
END=$(${print} '\033[0m')

# background
RN=$(${print} '\033[6;40m')
Rn=$(${print} '\033[40m')
RR=$(${print} '\033[6;41m')
Rr=$(${print} '\033[41m')
RG=$(${print} '\033[6;42m')
Rg=$(${print} '\033[42m')
RY=$(${print} '\033[6;43m')
Ry=$(${print} '\033[43m')
RB=$(${print} '\033[6;44m')
Rb=$(${print} '\033[44m')
RM=$(${print} '\033[6;45m')
Rm=$(${print} '\033[45m')
RC=$(${print} '\033[6;46m')
Rc=$(${print} '\033[46m')
RW=$(${print} '\033[6;47m')
Rw=$(${print} '\033[47m')

HIGH=$(tput bold)
SMUL=$(tput smul)
RMUL=$(tput rmul)
BLINK=$(tput blink)
REVERSE=$(tput smso)
REVERSO=$(tput rmso)
# text / foreground
n=$(tput setaf 0)
r=$(tput setaf 1)
g=$(tput setaf 2)
y=$(tput setaf 3)
b=$(tput setaf 4)
m=$(tput setaf 5)
c=$(tput setaf 6)
w=$(tput setaf 7)
N=$(tput setaf 8)
R=$(tput setaf 9)
G=$(tput setaf 10)
Y=$(tput setaf 11)
B=$(tput setaf 12)
M=$(tput setaf 13)
C=$(tput setaf 14)
W=$(tput setaf 15)
END=$(tput sgr0)

HIGH=$(tput bold)
SMUL=$(tput smul)
RMUL=$(tput rmul)
BLINK=$(tput blink)
REVERSE=$(tput smso)
REVERSO=$(tput rmso)

# background
Rn=$(tput setab 0)
Rr=$(tput setab 1)
Rg=$(tput setab 2)
Ry=$(tput setab 3)
Rb=$(tput setab 4)
Rm=$(tput setab 5)
Rc=$(tput setab 6)
Rw=$(tput setab 7)
RN=$(tput setab 8)
RR=$(tput setab 9)
RG=$(tput setab 10)
RY=$(tput setab 11)
RB=$(tput setab 12)
RM=$(tput setab 13)
RC=$(tput setab 14)
RW=$(tput setab 15)



COLORIZE='eval sed -e "s/{END}/${END}/g" -e "s/{HIGH}/${HIGH}/g" -e "s/{SMUL}/${SMUL}/g" -e "s/{RMUL}/${RMUL}/g" -e "s/{BLINK}/${BLINK}/g" -e "s/{REVERSE}/${REVERSE}/g" -e "s/{REVERSO}/${REVERSO}/g"'
LOWS=' -e "s/{n}/${n}/g" -e "s/{r}/${r}/g" -e "s/{g}/${g}/g" -e "s/{y}/${y}/g" -e "s/{b}/${b}/g" -e "s/{m}/${m}/g" -e "s/{c}/${c}/g" -e "s/{w}/${w}/g"'
HIGHS=' -e "s/{N}/${N}/g" -e "s/{R}/${R}/g" -e "s/{G}/${G}/g" -e "s/{Y}/${Y}/g" -e "s/{B}/${B}/g" -e "s/{M}/${M}/g" -e "s/{C}/${C}/g" -e "s/{W}/${W}/g"'
REVLOWS=' -e "s/{Rn}/${Rn}/g" -e "s/{Rr}/${Rr}/g" -e "s/{Rg}/${Rg}/g" -e "s/{Ry}/${Ry}/g" -e "s/{Rb}/${Rb}/g" -e "s/{Rm}/${Rm}/g" -e "s/{Rc}/${Rc}/g" -e "s/{Rw}/${Rw}/g"'
REVHIGHS=' -e "s/{RN}/${RN}/g" -e "s/{RR}/${RR}/g" -e "s/{RG}/${RG}/g" -e "s/{RY}/${RY}/g" -e "s/{RB}/${RB}/g" -e "s/{RM}/${RM}/g" -e "s/{RC}/${RC}/g" -e "s/{RW}/${RW}/g"'

set +a

2. egrepi

and the egrepi function, effective and elegant: color cycling between 8 or more colors (your needs) AND tested under 3 different unix OS, with comments :

# egrepi() egrep with 8 REVERSE cyclic colorations on regexps almost like egrep
# egrepi 
# current script will work for KSH88, KSH93, bash 2+, zsh, under AIX / Linux / SunOS
egrepi ()
# colorList=wBcgymrN                                                # KSH93 or bash 3+, not for AIX
# set -A color                                                  # needed with older sh
color[0]=$Rw; color[1]=$RB; color[2]=$Rc; color[3]=$Rg; color[4]=$Ry; color[5]=$Rm; color[6]=$Rr; color[7]=$RN; # this is the only one AIX solution
unset argsToGrep argsSedColor argsPerlColor

for arg in ${args}
    [ "${arg}" == "." ] && arg=\\.                              # if you wanna grep "."
    # color=R${colorList:((${RANDOM: -1:1})):1}                     # bash RANDOMized colors
    # color=R${colorList:$i:1} && let i++ && ((i==8)) && i=0                # KSH93 or bash 3+, not for AIX
    # argsSedColor="${argsSedColor} -e s#${arg}#$n${!color}&${w}#gI"            # AIX KSH88 do not recognise this fucking variable double expansion
    # argsSedColor="${argsSedColor} -e s#${arg}#$n${color[$i]}&${w}#gI"         # AIX neither do include sed with Ignore case
    argsPerlColor="${argsPerlColor}${argsPerlColor:+,}s#${arg}#$n${color[$i]}$&${END}#gi"   # So: gotta use perl
    let i+=1 && ((i==8)) && i=0                             # AIX KSH88 do not recognise "let i++"
# egrep -i "${argsToGrep}" | sed ${argsSedColor} | egrep -v "grep|sed"              # AIX sed incompatibility with Ignore case
# (($# > 0)) && (egrep -i "${argsToGrep}" | perl -p -e ${argsPerlColor}) || cat         # this line colors & grep the words, will NOT act as "tail -f"
(($# > 0)) && (perl -p -e ${argsPerlColor}) || cat                      # this line just colors the words

3. Usage

command | egrepi word1 .. wordN

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You might also want to take a look at lwatch:

tail -f /var/log/syslog | lwatch --input -

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Publishes some time ago Node Js utility - log-color-highlight

tail -f file | lch -red error warn -green success lch -f file -red.bold error warn -underline.bgGreen success

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As for the color codes, I would use tput:

red=$( tput -Txterm setaf 1 )
norm=$( tput -Txterm sgr0 )
bold=$( tput -Xterm bold )

Cf. man tput


tail -F myfile.log | sed "s/\(.ERROR.*\)/$red$bold\1$norm/g"
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