lists@xxxxxxxxxxx wrote:
> Hi,
>
> I was not having PHP on the machine I am reading this email for the
> moment. But I tried to use it together with egrep, but it didn't work.
> Maybe egrep is using different syntax for these lookaheads, but with
> other tests it has been working same as for preg_match in PHP. As you
> see the first simple example works, but fails when I insert the lookahead.
>
> [peternokia@localhost ~]$ echo 0123 | egrep '^[0-9]{4}$'
> 0123
> [peternokia@localhost ~]$ echo 0123 | egrep '^(?=.*2.*)[0-9]{4}$'
> [peternokia@localhost ~]$
>
I couldn't get egrep to work either but the following cmdline output
shows that the given regexp will do the job with preg_match:
tina:~# php -r ' echo preg_match("#^(?=\\d*8\\d*)[0-9]{4}\$#", "8123"),"\n"; '
1
tina:~# php -r ' echo preg_match("#^(?=\\d*8\\d*)[0-9]{4}\$#", "08123"),"\n"; '
0
tina:~# php -r ' echo preg_match("#^(?=\\d*8\\d*)[0-9]{4}\$#", "0812"),"\n"; '
1
tina:~# php -r ' echo preg_match("#^(?=\\d*8\\d*)[0-9]{4}\$#", "20812"),"\n"; '
0
tina:~# php -r ' echo preg_match("#^(?=\\d*8\\d*)[0-9]{4}\$#", "2081"),"\n"; '
1
tina:~# php -r ' echo preg_match("#^(?=\\d*8\\d*)[0-9]{4}\$#", "2008"),"\n"; '
1
> /Peter
>
>
>
> Quoting Martin Alterisio <malterisio777@xxxxxxxxx>:
>
>> PS: I think you can remove the last .*, leaving the assertion like this:
>> (?=.*8), and it will still work fine and probably faster (which dosen't
>> matter under these conditions). But I haven't tried that one (and have
>> already erased the test file I did to check the regular expression).
>>
>> 2007/2/9, Martin Alterisio <malterisio777@xxxxxxxxx>:
>>>
>>> If you want to do it in one regular expression, without listing each
>>> case,
>>> you can use a lookahead assertion:
>>>
>>> /^(?=.*8.*)[0-9]{4}$/
>>>
>>> The assertion (?=.*8.*) checks that the following matches the expression
>>> contained (.*8.*) which fails if there is not an 8.
>>>
>>> 2007/2/9, Peter Lauri <lists@xxxxxxxxxxx>:
>>>>
>>>> Best group member,
>>>>
>>>>
>>>>
>>>> I want to match a four digit number. I allow user to enter with *
>>>> syntax. So
>>>> 8* would match anything that starts with 8 and is 4 digit long so:
>>>>
>>>>
>>>>
>>>> /^8[0-9]{3}$/
>>>>
>>>>
>>>>
>>>> That was easy. Ok then my other case was: *8, so anything that ends
>>>> with
>>>> 8
>>>>
>>>>
>>>>
>>>> /^[0-9]{3}8$/
>>>>
>>>>
>>>>
>>>> Ok, now the tricky one comes: *8*, so match it incase 8 is anywhere in
>>>> the
>>>> number. Can be beginning, end or in the middle. The problem that I face
>>>> I
>>>> cannot find out a good way of doing this correctly. So I ended up with
>>>> an
>>>> expression like this:
>>>>
>>>>
>>>>
>>>> /^(8[0-9]{3}|[0-9]8[0-9]{2}|[0-9]{2}8[0-9]|[0-9]{3}8)$/
>>>>
>>>>
>>>>
>>>> This takes care of it and everything, BUT it is so ugly. What I
>>>> actually
>>>>
>>>> need to construct is: A regular expression that checks if 8 is a
>>>> part of
>>>> the
>>>> number, and then that it is four digit long.
>>>>
>>>>
>>>>
>>>> The pipe "|" is an OR operator, but are there not any "AND" operator in
>>>> Regular Expressions? I have been trying to figure this out for a while
>>>> now.
>>>> Of course I am using the above syntax right now, but would like to
>>>> strip
>>>> it
>>>> down. Maybe not for the performance, but for the beauty of it :-)
>>>>
>>>>
>>>>
>>>> If you have any comments and suggestions about this I would be happy.
>>>>
>>>>
>>>>
>>>> Best regards,
>>>>
>>>> Peter Lauri
>>>>
>>>>
>>>>
>>>> <http://www.dwsasia.com/> www.dwsasia.com - company web site
>>>>
>>>> <http://www.lauri.se/> www.lauri.se - personal web site
>>>>
>>>> < http://www.carbonfree.org.uk/> www.carbonfree.org.uk - become Carbon
>>>> Free
>>>>
>>>>
>>>>
>>>>
>>>
>
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