bashdash-shell

Bash vs. Dash behavior with the command `echo -ne "hello\n"`

I got different behaviors with the same command echo -ne "hello\n" with bash and with dash. See below :

$ bash -c 'echo -ne "hello\n"'
hello
$ dash -c 'echo -ne "hello\n"'
-ne hello

Why is that ? I don't understand at all…

My system : 

$ lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description:    Ubuntu 12.04.5 LTS
Release:    12.04
Codename:   precise
Solution

  • The POSIX specification for echo doesn't support any arguments. See it here.

    And while the spec mentions -n it does so to say that it is not an option and is either an implementation defined case or to be treated as a string.

    So dash is doing exactly that.

    bash, on the other hand, has non-conforming behavior in a number of ways.

    This is why the use of echo is generally discouraged in favor of the using printf which has a much better specification and much better portable behavior.