The use of '\e' isn't POSIX compliant.

[kkdd]

Hello,
I think that the use of '\e' should be warned by shellcheck to be non-POSIX compliant.

$ dash -c "printf '\e'" 
\e$ 
$ bash -c "printf '\e'" 
$ 
$ echo "printf '\e'" | shellcheck -s sh -
$ 
$ shellcheck -V
ShellCheck - shell script analysis tool
version: 0.10.0
license: GNU General Public License, version 3
website: https://www.shellcheck.net

[marilene38]

Thank you for raising this issue!

I agree that ShellCheck should emit a warning when \e is used with printf in POSIX mode. Since \e is not specified by POSIX, its behavior can vary between shells—for example, dash prints it literally, while bash interprets it as the escape character. This can lead to non-portable scripts and unexpected results.

Suggestion:
ShellCheck could display a warning such as:

Use of \e in printf is not POSIX-compliant and may behave differently across shells. Consider using \033 or \x1b for portability.

Flagging this usage would help users write more portable scripts and avoid subtle bugs. If maintainers are in agreement, updating the rule set to detect this in POSIX mode would be a valuable enhancement.