How to use printf and %s when there are color codes?

Question

I had these lines:

if [[ $# -eq 0 ]]; then
  printf "$fail_color Error - Function: $function, Line: $line_number \n"
  printf "do_test: Third parameter missing - expected result\n"
  exit 1
fi

This works fine and gives me the intended output of Error - Function: words, Line: 94

I then used ShellCheck and it recommended

printf "$fail_color Error - Function: $function, Line: $line_number \n
             ^––SC2059 Don't use variables in the printf format string. Use printf "..%s.." "$foo".

So I tried changing it to

  printf "%s Error - Function: %s, Line: %s \n", "$fail_color", "$function", "$line_number"

but now the output shows the color code details instead of the color:

\033[31;1m, Error - Function: words,, Line: 94 
,do_test: Third parameter missing - expected result

Related - is there a better way to name the strings other than multiple %s's?

Detail - the color are defined this way:

fail_color="\033[31;1m"
pass_color="\033[32;1m"
color_end="\033[0m"

Please [edit] your question and show us the contents of the variables and how they're being set. — terdon, May 25 '15 at 12:08

Cyrus · Answer 1 · 2021-03-16T18:25:02.183

10

fail="\033[31;1m"
color_end="\033[0m"
func="foo"  # (renamed this variable to avoid confusion with function keyword)
line_number="42"

printf "%bError - Function: %s, Line: %d%b\n" "$fail" "$func" "$line_number" "$color_end"

Output:

Error - Function: foo, Line: 42

Tested with Ubuntu 11.04 (bash 4.2.8(1)-release), Ubuntu 14.04.1 LTS (bash 4.3.11(1)-release), RHEL 5.1 (bash 3.1.17(1)-release), RHEL 6.0 (bash 4.1.2(1)-release), RHEL 7.0 (bash 4.3.11(1)-release) and Solaris 11 (bash 4.1.9(1)-release)

edited Mar 16 '21 at 18:25

answered May 25 '15 at 12:45

Cyrus

12,309

This didn't work for me. Maybe becuase I am using an include file for the color codes. However PM 2Ring's answer did work for me. – Michael Durrant May 25 '15 at 13:37
This code worked for me on Fedora 21:GNU bash, version 4.3.33(1)-release – somethingSomething May 25 '15 at 22:42

score 4 · Accepted Answer · answered May 25 '15 at 12:51

4

I like Cyrus's answer, but this syntax also works:

#!/usr/bin/env bash

fail_color=$'\033[31;1m'
color_end=$'\033[0m'
function="foo"
line_number="42"

printf "%sError - Function: %s, Line: %d%s\n" "$fail_color" "$function" "$line_number" "$color_end"

And ShellCheck says "It all looks good!". :)

answered May 25 '15 at 12:51

PM 2Ring

6,633

This is the only that has worked for me so far. – Michael Durrant May 25 '15 at 13:38
@MichaelDurrant Thanks! But it's odd that Cyrus's code didn't work. What version of bash are you using; FWIW, I'm using 4.1.5(1), with a ShellShock patch. – PM 2Ring May 25 '15 at 14:11
@PM2Ring this solution is not working with shell. Can you please assist? – ekassis Oct 22 '17 at 14:58
1

@ekassis "not working" is very vague. What does it do? Are you using Bash? If so, which version? What terminal are you using? – PM 2Ring Oct 22 '17 at 15:05
1

Note https://unix.stackexchange.com/q/371827/5132 of course. – JdeBP Dec 18 '19 at 13:06

score 0 · Answer 3 · edited Mar 06 '20 at 18:03

0

The printf(1) man says:

%b     ARGUMENT as a string with '\' escapes interpreted, except
       that octal escapes are of the form \0 or \0NNN

So, it`s works:

edited Mar 06 '20 at 18:03

Paulo Tomé

3,782

answered Mar 06 '20 at 17:23

Lasiar

1

Ned64 · Answer 4 · 2015-05-25T12:14:06.987

-2

The variable "$fail_color" contains one too many, or one too few backslashes before the 033, try changing it or removing the "" to have it debackslashified.

\033

is supposed to be the ESC character (ASCII 27 decimal, 033 octal).

edited May 25 '15 at 12:14

answered May 25 '15 at 11:55

Ned64

8,726

They work the other way and without them I get $ ./17_number_letter_counts.sh 033[31;1m, Error - Function: words,, Line: 94 ,do_test: Third parameter missing - expected result – Michael Durrant May 25 '15 at 12:01
OK, try adding a backslash instead of removing one - it is a little difficult to correct the code without actually seeing it or being able to call it oneself. Please also check the number of backslashes before the [ and ; characters. – Ned64 May 25 '15 at 12:06
I tried adding one, e.g. changing fail_color="\033[31;1m" to fail_color="\\033[31;1m" but I got the same error. – Michael Durrant May 25 '15 at 12:22
I meant trying also fail_color="\\033\[31\;1m (something like this has worked for me in the past) but I see that you have now found a different solution. – Ned64 May 25 '15 at 17:01

How to use printf and %s when there are color codes?

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