The (X) flag.

The (X) flag.

[Frank Terbeck]

Hi List.

Quoting the manual:

[snip]
 X  With this flag parsing errors occurring with the Q and  e  flags
    or  the  pattern  matching  forms  such as `${name#pattern}' are
    reported. Without the flag they are silently ignored.
[snap]

Now I thought it might throw an error when a given pattern doesn't
match:

[snip]
zsh% foo='Hello World, mere mortal!'
zsh% print ${foo#*, }               
mere mortal!
zsh% print ${foo#*. }
Hello World, mere mortal!
zsh% print ${(X)foo#*. }
Hello World, mere mortal!
[snap]

I would have expected an error for the last command.
However, I guess, I'm misunderstanding the manual. So, could someone
please give an example of what this flag does?

Regards, Frank

Re: The (X) flag.

[Bart Schaefer]

On Jun 28,  6:57am, Frank Terbeck wrote:
}
} Now I thought it might throw an error when a given pattern doesn't
} match:

No.  Failing to match the pattern is not an error, it's one of the
expected possible outcomes.

} However, I guess, I'm misunderstanding the manual. So, could someone
} please give an example of what this flag does?

The errors involved are lexical errors, that is, failures in tokenizing
the string.  I can't immediately think of one that affects ${var#pat},
but here's an obvious one with the (Q) flag:

    % foo="two ' matched ' quotes"
    % print ${(Q)foo}
    two  matched  quotes
    % foo="only one ' quote"
    % print ${(Q)foo}
    only one ' quote
    % print ${(XQ)foo}
    zsh: unmatched '
    % 

Re: The (X) flag.

[Frank Terbeck]

Bart Schaefer <schaefer@brasslantern.com>:
> On Jun 28,  6:57am, Frank Terbeck wrote:
> }
> } Now I thought it might throw an error when a given pattern doesn't
> } match:
> 
> No.  Failing to match the pattern is not an error, it's one of the
> expected possible outcomes.
> 
> } However, I guess, I'm misunderstanding the manual. So, could someone
> } please give an example of what this flag does?
> 
> The errors involved are lexical errors, that is, failures in tokenizing
> the string.  I can't immediately think of one that affects ${var#pat},
> but here's an obvious one with the (Q) flag:
[...]

Okay, that makes it a lot clearer for me.
Thank you.

Regards, Frank