Re: Doubt about expr

[Paul Eggert]

Eric Blake <address@hidden> writes:

> According to Sebastian Kreft on 9/12/2006 8:51 PM:
>> I don't know if it is a standard of expr, but I think that is not intuitive
>> to write a plus symbol before the string substr if I want to get the length
>> of it.
>
> POSIX states "The use of string arguments length, substr, index, or match
> produces unspecified results."
> (http://www.opengroup.org/onlinepubs/009695399/utilities/expr.html)  This
> is because these four strings can also be operators.

Also, POSIX does not specify these operators; it allows an
implementation that does not support these operators at all.
That's yet another reason why their use is nonportable.