How can I display the colors of text inserted with color codes by another program in Bash?

Question

When the text directly contained color code for example:

a="\033[0;31mRED\033[0m"
echo -e $a

The terminal had no problem colorizing the text in red. But when I modified the color code indirectly:

#!/bin/bash

# define color mappings
declare -A colors=(
    ['r']='\033[0;31m'  # Red (escaped for sed/printf)
    ['reset']='\033[0m'  # Reset color
)

# Sample text
t="abc def [ghi] jkl
nmo [ttt] dfd
and more"
# colorize all [...] in red
echo -e "$t" | sed "s/\(\[[^]]*\]\)/\\${colors[r]}\1\\${colors[reset]}/g"

The result was

abc def \033[0;31m[ghi]\033[0m jkl
nmo \033[0;31m[ttt]\033[0m dfd
and more

The terminal did not colorize [...]s with red color at all but showed the raw color codes. It seems like the problem is related to the timing of variable expansion of some sort.

choroba · Accepted Answer · 2025-10-31 18:12:11Z

3

The problem is not in variable expansion. The problem is you need echo -e to interpret the colour codes, but you run echo -e only for the original string. You then insert the colour codes, but this doesn't go through echo -e anymore. So, one way is to add it:

echo -e $(echo "$t" | sed "s/\(\[[^]]*\]\)/\\${colors[r]}\1\\${colors[reset]}/g" )

You can also store directly the colour codes, not their escaped variant. Then, you can directly output them without needing -e:

declare -A colors=(
    ['r']=$'\033[0;31m'   # <- See the dollar sign?
    ['reset']=$'\033[0m'  # <- It interprets the escape sequences.
)

The rest of the script can stay as it was, but you don't need -e for the output:

echo "$t" | sed "s/\(\[[^]]*\]\)/\\${colors[r]}\1\\${colors[reset]}/g"

answered Oct 31 at 18:12

choroba

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sseLtaH · Accepted Answer · 2025-10-31 18:33:52Z

0

You can call echo -e from within the sed command

$ sed "s/\[[^]]*]/$(echo -e ${colors[r]}\&${colors[reset]})/" <<< "$t"

Or, you could just use tput

sed -E "s/(\[)([^]]*)/\1$(tput setaf 1)\2$(tput sgr 0)/" <<< "$t"

answered Oct 31 at 18:33

sseLtaH

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Comments

Ed Morton · Accepted Answer · 2025-11-01 14:02:50Z

You might find an awk script more flexible than bash+sed, e.g.:

$ cat tst.sh
#!/usr/bin/env bash

t="abc {def} [ghi] 'jkl
nmo' [ttt] dfd
and {more}"

# colorize all [...] in red, '...' in blue, and '{...}' in green

awk '
    BEGIN {
        red    = "\033[1;31m"
        green  = "\033[1;32m"
        blue   = "\033[1;34m"
        reset  = "\033[0m"
    }
    { rec = rec $0 ORS }
    END {
        rec = highlight(rec, "[", "]", red)
        rec = highlight(rec, "\047", "\047", blue)
        rec = highlight(rec, "{", "}", green)
        printf "%s", rec
    }

    function highlight(tail, begChar, endChar, color,           head) {
        head = ""
        while ( match(tail, "[" begChar "][^" endChar "]+[" endChar "]") ) {
            head = head substr(tail,1,RSTART) color substr(tail,RSTART+1,RLENGTH-2) reset
            tail = substr(tail,RSTART+RLENGTH-1)
        }
        return head tail
    }
' <<<"$t"

Note that that's coloring multiple sections of input, including those that include newlines such as 'jkl<newline>nmo'.

See also the following for more examples of coloring with awk:

and this for shell:

tput-setaf-color-table-how-to-determine-color-codes

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