14

Lines 8. and 9. below confound me:

#!/bin/bash

a=foo
b=6
c=a
d="\e[33m"  # opening ansi color code for yellow text
e="\e[0m"   # ending ansi code
f=$d

printf "1. foo\n"
printf "2. $a\n"
printf "3. %s\n" "$a"
printf "4. %s\n" "${!c}"
printf "5. %${b}s\n" "$a"
printf "6. $d%s$e\n" "$a" # will be yellow
printf "7. $f%s$e\n" "$a" # will be yellow
printf '8. %s%s%s\n' "$d" "$a" "$e" # :(
printf "9. %s%s%s\n" "$f" "$a" "$e" # :(

Is it possible to use %s to expand a colour variable and see the colour switch?

Output:

1. foo
2. foo
3. foo
4. foo
5.    foo
6. foo
7. foo
8. \e[33mfoo\e[0m
9. \e[33mfoo\e[0m

Note: 6. and 7. are indeed yellow

Edit

printf "10. %b%s%b\n" "$f" "$a" "$e" # :)

... finally! That's the command that does it, thanks to Josh!

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2
  • 1
    It said "you need to wait 10 minutes to accept", so I made myself some coffee.. :)
    – Robottinosino
    Commented Apr 1, 2013 at 1:00
  • In final Edit: why $f instead of $d where f=$d (should be f="$d")
    – bvargo
    Commented Feb 28, 2023 at 17:31

2 Answers 2

Reset to default
22

You're looking for a format specifier that will expand escape characters in the argument. Conveniently, bash supports (from help printf):

%b        expand backslash escape sequences in the corresponding argument

Alternatively, bash also supports a special mechanism by which will perform expansion of escape characters:

d=$'\e[33m'
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  • success. bows in gratitude!
    – Robottinosino
    Commented Apr 1, 2013 at 0:45
  • Your point of declaring the variable as this: d=$'\e[33m' seems much finer that I had initially understood.. so, would you declare all colour escape sequences that way, then?
    – Robottinosino
    Commented Apr 1, 2013 at 0:52
2

I might I have what you were looking for. This script dumps out the ANSI printf sequences and the tput commands, along with sample text so you can see what it will look like.

#!/bin/bash

# Description: Used for testing the supported colors and printing the associated ANSI codes, or tput commands.

# Script / With Updates: https://github.com/lavabit/magma/blob/develop/dev/scripts/test/t.colors.sh
# Script / This Version: https://github.com/lavabit/magma/blob/eba6197e28dfe4464d483b1b068d17a1b18f1f3a/dev/scripts/test/t.colors.sh

echo
echo "$(tput bold)    ANSI COLORS$(tput sgr0)"

tput sgr0 ; printf "\n\e[0;1m      Text Modifiers\n\n" ; tput sgr0
printf "      T_BOLD=\"%s\"        \e[0;1m# SAMPLE TEXT\e[0;0m\n" "\e[0;1m"
printf "      T_ULINE=\"%s\"       \e[0;4m# SAMPLE TEXT\e[0;0m\n" "\e[0;4m"
printf "      T_STANDOUT=\"%s\"    \e[0;7m# SAMPLE TEXT\e[0;0m\n" "\e[0;7m"
printf "      T_RESET=\"%s\"       \e[0;0m# SAMPLE TEXT\e[0;0m\n" "\e[0;0m"

tput sgr0 ; printf "\n\e[0;1m      Foreground Colors\n\n" ; tput sgr0
printf "      T_BLK=\"%s\"        \e[0;30m# SAMPLE TEXT\e[0;0m\n" "\e[0;30m"
printf "      T_RED=\"%s\"        \e[0;31m# SAMPLE TEXT\e[0;0m\n" "\e[0;31m"
printf "      T_GRN=\"%s\"        \e[0;32m# SAMPLE TEXT\e[0;0m\n" "\e[0;32m"
printf "      T_YEL=\"%s\"        \e[0;33m# SAMPLE TEXT\e[0;0m\n" "\e[0;33m"
printf "      T_BLU=\"%s\"        \e[0;34m# SAMPLE TEXT\e[0;0m\n" "\e[0;34m"
printf "      T_MAG=\"%s\"        \e[0;35m# SAMPLE TEXT\e[0;0m\n" "\e[0;35m"
printf "      T_CYN=\"%s\"        \e[0;36m# SAMPLE TEXT\e[0;0m\n" "\e[0;36m"
printf "      T_WHT=\"%s\"        \e[0;37m# SAMPLE TEXT\e[0;0m\n" "\e[0;37m"

tput sgr0 ; printf "\n\e[0;1m      Foreground Colors (With Bold)\n\n" ; tput sgr0
printf "      T_BBLK=\"%s\"       \e[1;30m# SAMPLE TEXT\e[0;0m\n" "\e[1;30m"
printf "      T_BRED=\"%s\"       \e[1;31m# SAMPLE TEXT\e[0;0m\n" "\e[1;31m"
printf "      T_BGRN=\"%s\"       \e[1;32m# SAMPLE TEXT\e[0;0m\n" "\e[1;32m"
printf "      T_BYEL=\"%s\"       \e[1;33m# SAMPLE TEXT\e[0;0m\n" "\e[1;33m"
printf "      T_BBLU=\"%s\"       \e[1;34m# SAMPLE TEXT\e[0;0m\n" "\e[1;34m"
printf "      T_BMAG=\"%s\"       \e[1;35m# SAMPLE TEXT\e[0;0m\n" "\e[1;35m"
printf "      T_BCYN=\"%s\"       \e[1;36m# SAMPLE TEXT\e[0;0m\n" "\e[1;36m"
printf "      T_BWHT=\"%s\"       \e[1;37m# SAMPLE TEXT\e[0;0m\n" "\e[1;37m"

tput sgr0 ; printf "\n\e[0;1m      Foreground Colors (With Underline)\n\n" ; tput sgr0
printf "      T_UBLK=\"%s\"       \e[4;30m# SAMPLE TEXT\e[0;0m\n" "\e[4;30m"
printf "      T_URED=\"%s\"       \e[4;31m# SAMPLE TEXT\e[0;0m\n" "\e[4;31m"
printf "      T_UGRN=\"%s\"       \e[4;32m# SAMPLE TEXT\e[0;0m\n" "\e[4;32m"
printf "      T_UYEL=\"%s\"       \e[4;33m# SAMPLE TEXT\e[0;0m\n" "\e[4;33m"
printf "      T_UBLU=\"%s\"       \e[4;34m# SAMPLE TEXT\e[0;0m\n" "\e[4;34m"
printf "      T_UMAG=\"%s\"       \e[4;35m# SAMPLE TEXT\e[0;0m\n" "\e[4;35m"
printf "      T_UCYN=\"%s\"       \e[4;36m# SAMPLE TEXT\e[0;0m\n" "\e[4;36m"
printf "      T_UWHT=\"%s\"       \e[4;37m# SAMPLE TEXT\e[0;0m\n" "\e[4;37m"

tput sgr0 ; printf "\n\e[0;1m      Background Colors\n\n" ; tput sgr0
printf "      T_BLKB=\"%s\"         \e[40m# SAMPLE TEXT\e[0;0m\n" "\e[40m"
printf "      T_REDB=\"%s\"         \e[41m# SAMPLE TEXT\e[0;0m\n" "\e[41m"
printf "      T_GRNB=\"%s\"         \e[42m# SAMPLE TEXT\e[0;0m\n" "\e[42m"
printf "      T_YELB=\"%s\"         \e[43m# SAMPLE TEXT\e[0;0m\n" "\e[43m"
printf "      T_BLUB=\"%s\"         \e[44m# SAMPLE TEXT\e[0;0m\n" "\e[44m"
printf "      T_MAGB=\"%s\"         \e[45m# SAMPLE TEXT\e[0;0m\n" "\e[45m"
printf "      T_CYNB=\"%s\"         \e[46m# SAMPLE TEXT\e[0;0m\n" "\e[46m"
printf "      T_WHTB=\"%s\"         \e[47m# SAMPLE TEXT\e[0;0m\n" "\e[47m"

tput sgr0 ; printf "\n\e[0;1m      Background Colors (High Intensity)\n\n" ; tput sgr0
printf "      T_BLKHB=\"%s\"     \e[0;100m# SAMPLE TEXT\e[0;0m\n" "\e[0;100m"
printf "      T_REDHB=\"%s\"     \e[0;101m# SAMPLE TEXT\e[0;0m\n" "\e[0;101m"
printf "      T_GRNHB=\"%s\"     \e[0;102m# SAMPLE TEXT\e[0;0m\n" "\e[0;102m"
printf "      T_YELHB=\"%s\"     \e[0;103m# SAMPLE TEXT\e[0;0m\n" "\e[0;103m"
printf "      T_BLUHB=\"%s\"     \e[0;104m# SAMPLE TEXT\e[0;0m\n" "\e[0;104m"
printf "      T_MAGHB=\"%s\"     \e[0;105m# SAMPLE TEXT\e[0;0m\n" "\e[0;105m"
printf "      T_CYNHB=\"%s\"     \e[0;106m# SAMPLE TEXT\e[0;0m\n" "\e[0;106m"
printf "      T_WHTHB=\"%s\"     \e[0;107m# SAMPLE TEXT\e[0;0m\n" "\e[0;107m"

tput sgr0 ; printf "\n\e[0;1m      Foreground Colors (High Intensity)\n\n" ; tput sgr0
printf "      T_HBLK=\"%s\"       \e[0;90m# SAMPLE TEXT\e[0;0m\n" "\e[0;90m"
printf "      T_HRED=\"%s\"       \e[0;91m# SAMPLE TEXT\e[0;0m\n" "\e[0;91m"
printf "      T_HGRN=\"%s\"       \e[0;92m# SAMPLE TEXT\e[0;0m\n" "\e[0;92m"
printf "      T_HYEL=\"%s\"       \e[0;93m# SAMPLE TEXT\e[0;0m\n" "\e[0;93m"
printf "      T_HBLU=\"%s\"       \e[0;94m# SAMPLE TEXT\e[0;0m\n" "\e[0;94m"
printf "      T_HMAG=\"%s\"       \e[0;95m# SAMPLE TEXT\e[0;0m\n" "\e[0;95m"
printf "      T_HCYN=\"%s\"       \e[0;96m# SAMPLE TEXT\e[0;0m\n" "\e[0;96m"
printf "      T_HWHT=\"%s\"       \e[0;97m# SAMPLE TEXT\e[0;0m\n" "\e[0;97m"

tput sgr0 ; printf "\n\e[0;1m      Foreground Colors (High Intensity With Bold)\n\n" ; tput sgr0
printf "      T_BHBLK=\"%s\"      \e[1;90m# SAMPLE TEXT\e[0;0m\n" "\e[1;90m"
printf "      T_BHRED=\"%s\"      \e[1;91m# SAMPLE TEXT\e[0;0m\n" "\e[1;91m"
printf "      T_BHGRN=\"%s\"      \e[1;92m# SAMPLE TEXT\e[0;0m\n" "\e[1;92m"
printf "      T_BHYEL=\"%s\"      \e[1;93m# SAMPLE TEXT\e[0;0m\n" "\e[1;93m"
printf "      T_BHBLU=\"%s\"      \e[1;94m# SAMPLE TEXT\e[0;0m\n" "\e[1;94m"
printf "      T_BHMAG=\"%s\"      \e[1;95m# SAMPLE TEXT\e[0;0m\n" "\e[1;95m"
printf "      T_BHCYN=\"%s\"      \e[1;96m# SAMPLE TEXT\e[0;0m\n" "\e[1;96m"
printf "      T_BHWHT=\"%s\"      \e[1;97m# SAMPLE TEXT\e[0;0m\n" "\e[1;97m"

echo
echo "$(tput bold)    TPUT COLORS$(tput sgr0)"

# Text color variables
txtund=$(tput sgr 0 1)              # Underline
txtbld=$(tput bold)                   # Bold
bldred=${txtbld}$(tput setaf 1) #  Red
bldblu=${txtbld}$(tput setaf 4) #  Blue
bldwht=${txtbld}$(tput setaf 7) #  White
txtrst=$(tput sgr0)                   # Reset
info=${bldwht}*${txtrst}            # Feedback
pass=${bldblu}*${txtrst}
warn=${bldred}!${txtrst}

echo
echo "$(tput bold)      Text Modifiers$(tput sgr0)"
echo
echo '      Bold                    $(tput bold)'
echo '      Underline               $(tput sgr 0 1)'
echo '      Move Up / Delete        $(tput cuu1 ; tput dl1)'
echo '      Reset                   $(tput sgr0)'

echo
echo "$(tput bold)      Foreground Colors$(tput sgr0)"
echo
echo -e "$(tput bold)      reg  bld  und$(tput sgr0)"

for i in $(seq 1 7); do
  echo "      $(tput setaf $i)Text$(tput sgr0) $(tput bold)$(tput setaf $i)Text$(tput sgr0) $(tput sgr 0 1)$(tput setaf $i)Text$(tput sgr0)          \$(tput setaf $i)"
done

echo
echo "$(tput bold)      Background Colors$(tput sgr0)"
echo
echo -e "$(tput bold)      reg  bld  und$(tput sgr0)"

for i in $(seq 1 7); do
  echo "      $(tput setab $i)Text$(tput sgr0) $(tput bold)$(tput setab $i)Text$(tput sgr0) $(tput sgr 0 1)$(tput setab $i)Text$(tput sgr0)          \$(tput setab $i)"
done
echo
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