It's very easy to parse such strings, you just instruct the regex engine to save the Value part in $1 group variable.įor example, if the HTTP headers contain, HTTP headers are formatted as Key: Value pairs. Extract HTTP User-Agent string from the HTTP headers. The g flag makes sure it finds all the numbers in the string, and the e flag evaluates $1+1 as a Perl expression.įor example, this 1234 is awesome 444 gets turned into this 1235 is awesome 445.ġ16. It matches all integers (\d+), puts them in capture group 1, then it replaces them with their value incremented by one $1+1. Here we use the substitution operator s///. Increase all numbers by one in the string. Here the (word) captures the word in group 1 and \1 refers to contents of group 1, therefore it's almost the same as writing /(word).*word/įor example, silly things are silly matches /(silly).*\1/, but silly things are boring doesn't, because silly is not repeated in the string.ġ15. This regex matches word followed by something or nothing at all, followed by the same word.
Check if a word appears twice in the string. Next \d because of the same reasons as above.ġ14. The ^ at the beginning of regex is an anchor that matches the beginning of string. For example, it matches a valid IP 81.198.240.140 and it also matches an invalid IP such as 923.844.1.999. It matches a number followed by a dot four times. All it does is match something that looks like an IP. This regex doesn't guarantee that the thing that got matched is in fact a valid IP. Match something that looks like an IP address. You can also follow me on Twitter.Īwesome news: I have written an e-book based on this article series.
Reg exp perl pdf#
Part IX: Release of Perl One-Liners e-book.Īfter I am done with the next part of the article, I will release the whole article series as a pdf e-book! Please subscribe to my blog to be the first to get it.Part VII: Handy regular expressions (this part).Part VI: Selective printing and deleting of certain lines.Part V: Text conversion and substitution.Part IV: String creation and array creation.The article on Perl one-liners consists of nine parts: I will release the perl1line.txt in the next part of the series. Perl one-liners is my attempt to create " perl1line.txt" that is similar to " awk1line.txt" and " sed1line.txt" that have been so popular among Awk and Sed programmers, and Unix sysadmins. Please see part one for the introduction of the series. Perl is not Perl without regular expressions, therefore in this part I will come up with and explain various Perl regular expressions. This is the seventh part of a nine-part article on Perl one-liners.
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