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From 8-bit color chapter of Wikipedia's ANSI escape code, and to be quicker, without any loop:

#!/bin/bash shape='XXXXXXXX' arry=(0 0 2{,,}{,,}{,,,} 0{,,}) eval arry=(${arry[@]/?/\${shape:&\}}) printf -v shape '%s\n' "${arry[@]//X/ \\e[48;5;%d;38;5;%%%%dm C %%3d \\e[0m}" declare -ai arry=({0..255}) printf -v shape "$shape" ${arry[@]} printf -v shape "$shape" ${arry[@]} eval "arry=(${arry[@]/*/\"(&>231\&\&&<244)||((&<17)\&\&(&%8<2))||(&>16\&\&  &<232)\&\&((&-16)%6*11+(&-16)/6%6*14+(&-16)/36*10)<58?7:16\"})" printf "$shape" ${arry[@]} 

Note: this could by cut'n pasted into a fresh terminal window.

Same script with some comments:

#!/bin/bash # Building a shape of 41 lines with two first lines of 8 fields, followed # by 36 lines of 6 fields, then 3 lines of 8 fields. shape='XXXXXXXX' # an 8 X string arry=(0 0 2{,,}{,,}{,,,} 0{,,}) # 2(x8) + 36(x6) + 3(x8): 41 lines eval arry=(${arry[@]/?/\${shape:&\}}) # 'arry=(XXXXXXXX XXXXXXXX XXXXXX ...' printf -v shape '%s\n' "${arry[@]//X/ \\e[48;5;%d;38;5;%%%%dm C %%3d \\e[0m}" # %d will be ANSI color, then %%3d right aligned label, and %%%%d foreground declare -ai arry=({0..255}) # arry is now an array of 256 integers printf -v shape "$shape" ${arry[@]} # populate colors printf -v shape "$shape" ${arry[@]} # populate labels # Building array of 256 foreground colors eval "arry=(${arry[@]/*/\"(&>231\&\&&<244)||((&<17)\&\&(&%8<2))||(&>16\&\& &<232)\&\&((&-16)%6*11+(&-16)/6%6*14+(&-16)/36*10)<58?7:16\"})" printf "$shape" ${arry[@]} # print out finalised shape with foregrounds 

From 8-bit color chapter of Wikipedia's ANSI escape code:

#!/bin/bash for ((i=0; i<256; i++)) ;do  fg=$((((i>231&&i<244)||((i<17)&&(i%8<2))||(i>16&&i<232)&&((i-16)%6*11+  (i-16)/6%6*14+(i-16)/36*10)<58)?7:16)) printf ' \e[48;5;%d;38;5;%dm C %3d \e[49;39m' $i $fg $i  (( ((i<16||i>231) && ((i+1)%8==0)) || ((i>16&&i<232)&& ((i-15)%6==0)) )) &&  printf "\n" done 

Note: On my raspberry, this script take approx 1.5 seconds to complete.

Same but without loop:

Could be quicker again:

#!/bin/bash shape='XXXXXXXX' arry=(0 0 2{,,}{,,}{,,,} 0{,,}) eval arry=(${arry[@]/?/\${shape:&\}}) printf -v shape '%s\n' "${arry[@]//X/ \\e[48;5;%d;38;5;%%%%dm C %%3d \\e[0m}" declare -ai arry=({0..255}) printf -v shape "$shape" ${arry[@]} printf -v shape "$shape" ${arry[@]} eval "arry=(${arry[@]/*/\"(&>231\&\&&<244)||((&<17)\&\&(&%8<2))||(&>16\&\& &<232)\&\&((&-16)%6*11+(&-16)/6%6*14+(&-16)/36*10)<58?7:16\"})" printf "$shape" ${arry[@]} 

Note: this could by cut'n pasted into a fresh terminal window.

Then this version will print same output, but in ~0.6 second on my raspberry pi.

Explained:

• Building a shape of 41 lines with two first lines of 8 fields, followed by 36 lines of 6 fields, then 3 lines of 8 fields.

   shape='XXXXXXXX' # some 8 X string arry=(0 0 2{,,}{,,}{,,,} 0{,,}) # 2(x8) + 36(x6) + 3(x8): 41 lines eval arry=(${arry[@]/?/\${shape:&\}}) # 'arry=(XXXXXXXX XXXXXXXX XXXXXX ..' printf -v shape '%s\n' "${arry[@]//X/ \\e[48;5;%d;38;5;%%%%dm C %%3d \\e[0m}" 

  • replace each X by a format string for 3 values:
  • add a newline \n after each group of transformed X
  • %d will be ANSI color resolved first, then
  • %%3d for right aligned label, and
  • %%%%d for the foreground color.
• Converting $arry into an integer array containing values from 0 to 255

  declare -ai arry=({0..255}) 

• Populate background colors (%d)

   printf -v shape "$shape" ${arry[@]} 

• Populate labels (%%d)

   printf -v shape "$shape" ${arry[@]} 

• Compute 256 foreground colors into (integer) array $arry

   eval "arry=(${arry[@]/*/\"(&>231\&\&&<244)||((&<17)\&\&(&%8<2))||(&>16\&\& &<232)\&\&((&-16)%6*11+(&-16)/6%6*14+(&-16)/36*10)<58?7:16\"})" 

• Populate finalised shape with foregrounds and print out.

   printf "$shape" ${arry[@]} 

Preamble: about $TERM variable

echo $TERM xterm tput colors 8 

export TERM=xterm-256color ; reset tput colors 256 

Doing simply the job by using tput

#!/bin/bash for ((i=0; i<256; i++)) ;do echo -n ' ' tput setab $i tput setaf $(( ( (i>231&&i<244 ) || ( (i<17)&& (i%8<2)) || (i>16&&i<232)&& ((i-16)%6 <(i<100?3:2) ) && ((i-16)%36<15) )?7:16)) printf " C %03d " $i tput op (( ((i<16||i>231) && ((i+1)%8==0)) || ((i>16&&i<232)&& ((i-15)%6==0)) )) && printf "\n" '' done 

Could render something like:

Optimizing bash: reducing forks by running tput as background process

#!/bin/bash # Connector fifos directory read TMPDIR < <(mktemp -d /dev/shm/conn_shell_XXXXXXX) fd=3 # find next free fd nextFd() { while [ -e /dev/fd/$fd ];do ((fd++)) ;done;printf -v $1 %d $fd;} tputConnector() { mkfifo $TMPDIR/tput nextFd TPUTIN eval "exec $TPUTIN> >(LANG=C exec stdbuf -o0 tput -S - >$TMPDIR/tput 2>&1)" nextFd TPUTOUT eval "exec $TPUTOUT<$TMPDIR/tput" rm $TMPDIR/tput rmdir $TMPDIR } myTput() { echo -e "$1\ncr" 1>&$TPUTIN && IFS= read -r -d $'\r' -u $TPUTOUT $2 } tputConnector myTput op op myTput "setaf 7" grey myTput "setaf 16" black fore=("$black" "$grey") for ((i=0; i<256; i++)) ;do myTput "setab $i" bgr printf " %s%s %3d %s" "$bgr" "${fore[ i>231 && i<244||(i<17)&& (i%8<2)|| (i>16&&i<232)&&((i-16)%6*11+(i-16)/6%6*14+(i-16)/36*10)<58 ? 1 : 0 ]}" $i "$op" (( ((i<16||i>231) && ((i+1)%8==0)) || ((i>16&&i<232)&& ((i-15)%6==0)) )) && printf "\n" '' done 

While second script run in ~0.11 second on my desk and ~4.97 seconds on my raspberry.

Preamble: about $TERM variable

echo $TERM xterm tput colors 8 

export TERM=xterm-256color ; reset tput colors 256 

Doing simply the job by using tput

#!/bin/bash for ((i=0; i<256; i++)) ;do echo -n ' ' tput setab $i tput setaf $(( ( ( i > 231 && i < 244 ) || ( ( i < 17 ) && ( i % 8 < 2 ) ) || ( i > 16 && i < 232 ) && ( ( i - 16 ) % 6 * 11 + ( i - 16 ) / 6 % 6 * 14 + ( i - 16 ) / 36 * 10 ) < 58 ) ? 7 : 16 )) printf " C %3d " $i tput op (( ((i<16||i>231) && ((i+1)%8==0)) || ((i>16&&i<232)&& ((i-15)%6==0)) )) && printf "\n" done 

Should render something like:

Optimizing bash: reducing forks by running tput as background process

#!/bin/bash # Connector fifos directory read TMPDIR < <(mktemp -d /dev/shm/conn_shell_XXXXXXX) fd=3 # find next free fd nextFd() { while [ -e /dev/fd/$fd ];do ((fd++)) ;done;printf -v $1 %d $fd;} tputConnector() { mkfifo $TMPDIR/tput nextFd TPUTIN eval "exec $TPUTIN> >(LANG=C exec stdbuf -o0 tput -S - >$TMPDIR/tput 2>&1)" nextFd TPUTOUT eval "exec $TPUTOUT<$TMPDIR/tput" rm $TMPDIR/tput rmdir $TMPDIR } myTput() { echo -e "$1\ncr" 1>&$TPUTIN && IFS= read -r -d $'\r' -u $TPUTOUT $2 } tputConnector myTput op op myTput "setaf 7" grey myTput "setaf 16" black fore=("$black" "$grey") for ((i=0; i<256; i++)) ;do myTput "setab $i" bgr printf " %s%s %3d %s" "$bgr" "${fore[ i>231 && i<244||(i<17)&& (i%8<2)|| (i>16&&i<232)&&((i-16)%6*11+(i-16)/6%6*14+(i-16)/36*10)<58 ? 1 : 0 ]}" $i "$op" (( ((i<16||i>231) && ((i+1)%8==0)) || ((i>16&&i<232)&& ((i-15)%6==0)) )) && printf "\n" '' done 

While second script run in ~0.11 second on my desk and ~4.97 seconds on my raspberry.

Without forks, using ansi sequences

From 8-bit color chapter of Wikipedia's ANSI escape code, and to be quicker, without any loop:

#!/bin/bash shape='XXXXXXXX' arry=(0 0 2{,,}{,,}{,,,} 0{,,}) eval arry=(${arry[@]/?/\${shape:&\}}) printf -v shape '%s\n' "${arry[@]//X/ \\e[48;5;%d;38;5;%%%%dm C %%3d \\e[0m}" declare -ai arry=({0..255}) printf -v shape "$shape" ${arry[@]} printf -v shape "$shape" ${arry[@]} eval "arry=(${arry[@]/*/\"(&>231\&\&&<244)||((&<17)\&\&(&%8<2))||(&>16\&\& &<232)\&\&((&-16)%6*11+(&-16)/6%6*14+(&-16)/36*10)<58?7:16\"})" printf "$shape" ${arry[@]} 

Note: this could by cut'n pasted into a fresh terminal window.

Same script with some comments:

#!/bin/bash # Building a shape of 41 lines with two first lines of 8 fields, followed # by 36 lines of 6 fields, then 3 lines of 8 fields. shape='XXXXXXXX' # an 8 X string arry=(0 0 2{,,}{,,}{,,,} 0{,,}) # 2(x8) + 36(x6) + 3(x8): 41 lines eval arry=(${arry[@]/?/\${shape:&\}}) # 'arry=(XXXXXXXX XXXXXXXX XXXXXX ...' printf -v shape '%s\n' "${arry[@]//X/ \\e[48;5;%d;38;5;%%%%dm C %%3d \\e[0m}" # %d will be ANSI color, then %%3d right aligned label, and %%%%d foreground declare -ai arry=({0..255}) # arry is now an array of 256 integers printf -v shape "$shape" ${arry[@]} # populate colors printf -v shape "$shape" ${arry[@]} # populate labels # Building array of 256 foreground colors eval "arry=(${arry[@]/*/\"(&>231\&\&&<244)||((&<17)\&\&(&%8<2))||(&>16\&\& &<232)\&\&((&-16)%6*11+(&-16)/6%6*14+(&-16)/36*10)<58?7:16\"})" printf "$shape" ${arry[@]} # print out finalised shape with foregrounds 

Note: as this don't refer to tput, environment variable TERM doesn't matter.

Optimizing bash: reducing forks by running backgroung task

Optimizing bash: reducing forks by running tput as background process