I have come across a question from colleague about complex regex, so I written a regex using grep's -P option in PCRE regex. Since its a new learning for me, so thought to share with forums.
Lets say we have a Input_file with following test data:
Now conditions here are first keyword project is fixed but could be in any case, then versions side is the main thing which we need to get as an output. In versions apart from first major version all can have alphabets also.
So I have come up with:
Explanation of above code:
-i: means ignore case for grep which will help us to match any kind of Project string in lines. -o: means give only exact match of the line. -P: means it enables PCRE regex suite for grep, which has all kind of regex mechanism in it.
Now coming to main code part:
project\D+: Look for string project(in any case) till all NON digits value(\D denotes it). \K: means forget all previous matches this is a GREAT feature of grep and I LOVED it d+\.([\d,a-z,A-Z]+\.){1,}[\d,a-z,A-Z]+|\d+\.[\d,a-z,A-Z]+|\d+: Here I am matching digits OR digits with alphabets with one or more occurences and only digits too for all lines, to cover all kind of cases.
Since after \k( denotes the match which should be printed so it will print only matched part in lines.
I am still learning PCRE regex, any suggestions, improvements are super allowed
Cheers and Happy learning.
Thanks,
R. Singh
This User Gave Thanks to RavinderSingh13 For This Post:
Hi
It's a bit redundant
option -i applies to the whole template
if you want to limit it is better so
Hello Nez,
Cool; thanks for letting your views , but IMHO why I added that checks in case version is in some other format then it shouldn't have false positive in output.
Thanks,
R. Singh
This User Gave Thanks to RavinderSingh13 For This Post:
Learnt an example of Lazy match in Regex in Perl, so thought to share here.
Let's say following is Input_file.
Now we would like to have data between first occurrence of ^ to DUMMY , then we could use Lazy match like as follows:
Output will be as follows for mentioned sample:
Why is Lazy match Good here? Because .* is a GREEDY match and matches anything till last occurrence of any mentioned character etc but using Lazy match .*?DUMMY\s+ it matches very first occurrence of string DUMMY followed with space starting from ^
Tested and written this in PERL, thought/views/improvements are most welcome here.
Thanks,
R. Singh
This User Gave Thanks to RavinderSingh13 For This Post:
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LOCAL_CONFIG
#
Kcheckaddress regex -a@MATCH
+<@+?\.++?\.(us|info|to|br|bid|cn|ru)
LOCAL_RULESETS
SLocal_check_mail
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