if loop

[Allanm]

Can someone please explain the if loop here used in a perl script :

if (m!\[(\d+)\]!)

Thanks,
Allan

[Venkatesh BL]

Am not a perl guy, but, looks like a pattern check...did u try google?

[Peter Nikitka]

Hi,

the if-condition ('if' is not loop) is true when matching a number in square brackets, like [12].

mfG Peter

[Allanm]

Thanks for replying Peter, please find attached the exact script. Could you please explain what its doing. I am not understanding the if conditions here.

Thanks.
Allan

[Peter Nikitka]

Hi,

I suspect this scripts tries to hack a website.
Is that really your idea?

mfG Peter

[James R. Ferguson · Accepted solution]

Hi:

This is a test for a match using a regular expression.

The 'm' means match. Perl allows many different delimiters to bracket the match and in this case the '!' character was chosen.

The opening ('[') and closing (']') bracket characters are escaped with a backslash so that they represent themselves in the match and not a character class.

The '\d+' stands for a digit that occurs one or more times but at least once.

The parentheses () surrounding the '\d+' tell the regular expression engine to capture any match it finds therein. The outer parentheses are syntax for the 'if' condition.

In all, the condition is true (a match) if the variable ($_) --- often a line read --- looks like:

[123]

If you do:

# perl -nle 'print $1 if (m!\[(\d+)\]!)'

...then you will see the digits that are surrounded by the square brackets echoed for every input that matches.

Regards!

...JRF...

[Allanm]

Thanks JRF , appreciate it!