In Regular Expression

[cnsabar]

Hi.,

Anyone please tell me the difference of using (.*) and (.*?) in a regular expression.

While programming I am in confuse when using this..

If anyone help me with examples or suggesting any sites it will be useful for me

Thanks

[numberwhun]

Hi.,

Anyone please tell me the difference of using (.*) and (.*?) in a regular expression.

While programming I am in confuse when using this..

If anyone help me with examples or suggesting any sites it will be useful for me

Thanks

Is that the whole of the regular expression? Is there more to it?

The dot matches any single character except a newline and the asterisk is a modifier that says to match the preceding element 0 or more times. The question mark is also a modifier that says to match the preceding element 0 or 1 times.

Basically, this regex is matching any character (except newline) zero or more times and then matches that zero or one times. You shoudn't need the ? in there if you ask me unless the data being matched would call for it, but I don't see why. We would need to see the data being matched and the rest of the regex, if there is more, to be able to tell you more.

Regards,

Jeff

[KevinADC]

Is that the whole of the regular expression? Is there more to it?

The dot matches any single character except a newline and the asterisk is a modifier that says to match the preceding element 0 or more times. The question mark is also a modifier that says to match the preceding element 0 or 1 times.

Basically, this regex is matching any character (except newline) zero or more times and then matches that zero or one times. You shoudn't need the ? in there if you ask me unless the data being matched would call for it, but I don't see why. We would need to see the data being matched and the rest of the regex, if there is more, to be able to tell you more.

Regards,

Jeff

In this context the ? is beig used to make the pattern match as little as possible instead of matching as much as possible: non-greedy matching. But it would only work if there is more to the regexp, for example:

$foo = 'this,is,a,test';
$foo =~ /(.*),(.*)/;
$foo =~ /(.*?),(.*)/;
 

In the first regexp, the first set of parenthesis will match until the last comma in the string (greedy matching): this,is,a and the second set of parenthesis will match: test

In the second regexp, the first set of parenthesis will match until the first comma (non-greedy matching): this and the second set of parenthesis will match everything after the first comma (greedy matching): is,a,test

[cnsabar]

Hi Jeff and Kevin.,

Thanks for your notes with examples..
Now I understood the difference of using (.*) and (.*?)

Also I would like to know further regarding this more in other possible cases.
If you come across to know any sites with tutorial about this..
Please provide me the link ...

It will be useful for me also..
Thanks a lot.

[mohanprasadgutta]

.* should be used for greedy search.
.*? should be used for non greedy search.

[t3chn0n3rd]

The question mark matches one character as below


Hello
?ello

The asterisk matches many , such as

H*
Hello

It would seem that * followed by a ? would be redundant


H*?
Hello

[KevinADC]

The question mark matches one character as below


Hello
?ello

The asterisk matches many , such as

H*
Hello

It would seem that * followed by a ? would be redundant


H*?
Hello

You seem confused. Read a good perl regular expression tutorial to understand what the ? is used for and how its meaning changes depending on context.