Re: string equal problem

[Frank Terbeck <ft@xxxxxxxxxxxxxxxxxxx>]

Frank Terbeck wrote:
> Lyre wrote:
>> To my surprise，the following statment:
>>
>> if [ "abc" == "def" ]; then echo y; else echo n; fi
>>
>> doesn't work, it says "zsh: = not found".
>
> `==' only works in "[[ ... ]]". [...]

Actually, that's not quite true.

`[' works like a command, thus == is seen like it is for any other
command too. And in those cases, the leading equal leads to expansion of
the corresponding program's full path. For example

zsh% print =emacs
/usr/bin/emacs

Now, there is no command "=" on your system, which is why you're getting
the correct message "= not found". To prevent this, you can either unset
the `EQUALS' option (man zshoptions | less -p EQUALS) or quote the
string that is otherwise subject to this expansion. As in:

       if [ 'abc' '==' 'def' ]; then

Regards, Frank

-- 
In protocol design, perfection has been reached not when there is
nothing left to add, but when there is nothing left to take away.
                                                  -- RFC 1925