Use echo options when execution shell script

Question

On mac OSX, I have this script:

#!/usr/local/bin/bash
echo -e "\e[41mError: Some error.\e[0m"

When I just run the echo -e ... in a console, it prints the colored text "Error: Some error."

When executed as a script sh myscript.sh, it litterally prints the flag and the escape characters: -e "\e[41mError: Some error.\e[0m".

When I add the script location to ~/.bash_profile and execute it as myscript.sh, it does work. But I need to be able execute it without adding it to my bash profile.

Edit: using printf works: printf "\e[41mError: Some error.\e[0m\n".

Not sure where you'd find that escape sequence, but use #!/bin/bash as shebang, then use echo -e '\033[0;31mError: Some Error.\033[0m' and call it with ./script.sh — 0stone0
– 0stone0, Commented Jan 31, 2022 at 10:56
Side note: if adding colour and other terminal control sequences to a shell script, it's good practise to only do it if the output file descriptor actually refers to a terminal. This allows the sequences to be excluded when piping to a filter, or capturing to a file. You can test if output is to a terminal: test -t 2 for stderr. I like to implement this by using variables for the control sequences (like red_2='\e[41m'), and then only set them if the test returns true for that fd. — dan
– dan, Commented Jan 31, 2022 at 11:53
Different versions of echo behave differently when parsing options and/or escape sequences; I had a bunch of my scripts break when Mac OS X 10.5 (I think that was the version) came out and its bash built-in changed behavior(!). printf is more complex to use properly (its first argument is a format string that's used to control how the rest of the arguments are printed), but it's way more predictable. For this, I'd use printf '\e[41m%s\e[0m' "Error: Some error.". See this and this. — Gordon Davisson
– Gordon Davisson, Commented Jan 31, 2022 at 17:43

Thomas Dignan · Accepted Answer · 2022-01-31 11:05:58Z

1

when you run the shell with sh it runs in posix compatibility mode (i.e. as the bourne shell does)

bash is a successor to this shell, one of the features it adds is the -e switch to echo

in posix shell you don't need the -e, the escapes will be evaluated anyway

in bash you do, so if you want to run bash do so explicitly

answered Jan 31, 2022 at 11:05

Thomas Dignan

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