Bug or unwanted behaviour in echo ?

Hello list,


First of all, my apologies if this issue was already raised and
discussed, I haven't found it so far.


I was toying around with a site that proposed to hash passwords to
MD5, and comparing results with my host running FreeBSD 7.0-STABLE

At some point I didn't get the same hash from the website and from BSD.

On BSD:
echo -n "test'$_at_" | md5
5c28a8c6d799d302f3ef53afefdfc81b

On website:
f883cdacbb478c241c51da1f67fbe9bf

After swapping characters around I realized that echo just interprets
$_at_ (which in our case is null).


So I tried escaping the _at_ which didn't work:
echo -n "test'$\_at_" | md5
cff4781da603112b5a271891c7c9cc47

Escaping the $ did work however:
echo -n "test'\$_at_" | md5
f883cdacbb478c241c51da1f67fbe9bf



I can not think of a concrete example at the moment, but I can imagine
a program creating a hash and inadvertently feeding md5 a string
containing $? , $_at_ , $# or $1 for example.
This could lead to unwanted results.



Anyone knows if this behaviour is intended ?
It sure confused me here.

Perhaps a switch should be added to tell echo to not parse the $variables ?
Or perhaps it should be the natural behaviour to not parse them, and
only do it if -e was given ?


Regards,