Output in color - Bash

Question

I have seen several answers but they all talk about echo. How can I change the color of an output of a command in bash? For instance, I want to colorize the output of hostname command.

$ hostname 
Nameofcomputer <--- Just the output to be colored and then it returns to default color of the shell.

Solution 1

There are programs that will already do this for you, like grc, it's a

generic colouriser, can be used to colourise logfiles, output of commands, arbitrary text.... configured via regexp's.

_{[I normally don't like to use an image of text, but I don't think StackExchange has colour fomrat options]}

Or there's also source-highlight.

See Is there colorizer utility that can take command output and colorize it accordingly to pre-defined scheme? on SuperUser too

Solution 2

This is a partial answer that works in general, but chokes on special characters.

#!/bin/sh

case $1 in
  red)     col=$'\e[1;31m' ;;
  green)   col=$'\e[1;32m' ;;
  yellow)  col=$'\e[1;33m' ;;
  blue)    col=$'\e[1;34m' ;;
  magenta) col=$'\e[1;35m' ;;
  cyan)    col=$'\e[1;36m' ;;
esac

printf "%s" "${col}"

shift
eval $@

Usage

Presuming it's called set-color, simply call it with set-color red hostname.

Explanation

• The case block defines the colours, as per jasonwryan's answer here.
• The script sets this colour with printf.
• shift removes the first option fed to the script (i.e. the colour).
• eval $@ then executes the rest of the script.

Problem

The problem is that the script eats up the escapes and quotations marks. e.g. if you normally executed.

grep "foo bar" file\ name

Then you'd have to use

set-color red grep \"foo bar\" file\\ name

Solution 3

tput setaf 1; hostname; tput sgr0

tput queries the terminal database for the corresponding capability. Here setaf for set ANSI colour 1 (red), sgr0 to select graphic rendition none to go back to default attributes. Instead of tput sgr0, you can also use tput op (original pair) to only reset background and foreground colour and leave other graphic attributes (bold, underline, standout, reverse...) alone.

Some shells like zsh, tcsh or fish have builtin support to query that database or map color names to ANSI codes (like zsh or fish), but not bash.

In zsh, using prompt expansion to print the hostname in red:

print -P '%F{red}%m%f'

(%f only resets the foreground colour)

In tcsh or zsh with the echotc builtin using termcap codes instead of terminfo:

echotc AF 1; hostname; echotc me

(zsh has echoti for the terminfo codes setab/sgr0 like modern versions of tput).

In zsh, the % parameter expansion flag turns on prompt expansion upon parameter expansion, so you can do:

red=%F{red} normal=%f

echo ${(%)red}whatever%{(%)normal}

In zsh, you'll also find a colors autoloadable function that you can run to have helpers to write things in colour:

autoload colors; colors

echo $fg[red]whatever$fg[default]

Comments

[Jeff Schaller]

wouldn't quoting "$@" help?

[Sparhawk]

@JeffSchaller It doesn't seem to. :(