How to change the output color of echo in Linux

Question

I am trying to print a text in the terminal using echo command.

I want to print the text in a red color. How can I do that?

Answer 1

This is the color switch \033[. See history.

Color codes are like 1;32 (Light Green), 0;34 (Blue), 1;34 (Light Blue), etc.

We terminate color sequences with a color switch \033[ and 0m, the no-color code. Just like opening and closing tabs in a markup language.

  SWITCH="\033["
  NORMAL="${SWITCH}0m"
  YELLOW="${SWITCH}1;33m"
  echo "${YELLOW}hello, yellow${NORMAL}"

Simple color echo function solution:

cecho() {
  local code="\033["
  case "$1" in
    black  | bk) color="${code}0;30m";;
    red    |  r) color="${code}1;31m";;
    green  |  g) color="${code}1;32m";;
    yellow |  y) color="${code}1;33m";;
    blue   |  b) color="${code}1;34m";;
    purple |  p) color="${code}1;35m";;
    cyan   |  c) color="${code}1;36m";;
    gray   | gr) color="${code}0;37m";;
    *) local text="$1"
  esac
  [ -z "$text" ] && local text="$color$2${code}0m"
  echo "$text"
}

cecho "Normal"
cecho y "Yellow!"

Answer 2

Use tput to calculate color codes. Avoid using the ANSI escape code (e.g. \E[31;1m for red) because it's less portable. Bash on OS X, for example, does not support it.

BLACK=`tput setaf 0`
RED=`tput setaf 1`
GREEN=`tput setaf 2`
YELLOW=`tput setaf 3`
BLUE=`tput setaf 4`
MAGENTA=`tput setaf 5`
CYAN=`tput setaf 6`
WHITE=`tput setaf 7`

BOLD=`tput bold`
RESET=`tput sgr0`

echo -e "hello ${RED}some red text${RESET} world"

Answer 3

For readability

If you want to improve the readability of the code, you can echo the string first then add the color later by using sed:

echo 'Hello World!' | sed $'s/World/\e[1m&\e[0m/' 

Answer 4

To expand on this answer, for the lazy of us:

function echocolor() { # $1 = string
    COLOR='\033[1;33m'
    NC='\033[0m'
    printf "${COLOR}$1${NC}\n"
}

echo "This won't be colored"
echocolor "This will be colorful"

Answer 5

Inspired by @nachoparker's answer, I have this in my .bashrc:

#### colours
source xcol.sh

### tput foreground
export tpfn=$'\e[0m' # normal
export tpfb=$(tput bold)

## normal colours
export tpf0=$(tput setaf 0) # black
export tpf1=$(tput setaf 1) # red
export tpf2=$(tput setaf 2) # green
export tpf3=$(tput setaf 3) # yellow
export tpf4=$(tput setaf 4) # blue
export tpf5=$(tput setaf 5) # magenta
export tpf6=$(tput setaf 6) # cyan
export tpf7=$(tput setaf 7) # white
# echo "${tpf0}black ${tpf1}red ${tpf2}green ${tpf3}yellow ${tpf4}blue ${tpf5}magenta ${tpf6}cyan ${tpf7}white${tpfn}"

## bold colours
export tpf0b="$tpfb$tpf0" # bold black
export tpf1b="$tpfb$tpf1" # bold red
export tpf2b="$tpfb$tpf2" # bold green
export tpf3b="$tpfb$tpf3" # bold yellow
export tpf4b="$tpfb$tpf4" # bold blue
export tpf5b="$tpfb$tpf5" # bold magenta
export tpf6b="$tpfb$tpf6" # bold cyan
export tpf7b="$tpfb$tpf7" # bold white
# echo "${tpf0b}black ${tpf1b}red ${tpf2b}green ${tpf3b}yellow ${tpf4b}blue ${tpf5b}magenta ${tpf6b}cyan ${tpf7b}white${tpfn}"

The export allows me to use those tpf.. in Bash scripts.

Answer 6

I instead of hard coding escape codes that are specific to your current terminal, you should use tput.

This is my favorite demo script:

#!/bin/bash

tput init

end=$(( $(tput colors)-1 ))
w=8
for c in $(seq 0 $end); do
    eval "$(printf "tput setaf %3s   " "$c")"; echo -n "$_"
    [[ $c -ge $(( w*2 )) ]] && offset=2 || offset=0
    [[ $(((c+offset) % (w-offset))) -eq $(((w-offset)-1)) ]] && echo
done

tput init