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18:31:30,859 root INFO insert req into server queue 18:31:30,861 root DEBUG start consume requests from server queue Request:, URI: –PWgJuTrmAX1A3jeoyAgAAAAADAQAX1AQUZm52OkJCMjg1QTQ**, Payload: 18:31:30,788 access INFO request accepted. The word which I am trying to find is ––PWgJuTrmAX1A3jeoyAgAAAAADAQAX1AQUZm52OkJCMjg1QTQ But somehow grep is not returning the line which contains it. I am passing name of file from command line and also the word which I want to find through command line and print those lines which contains that word. I have a logfile say logfile.txt which contains info. Open(HANDLE, = grep /\Q$DeviceURI\E/, $subarray.”\n”
![grep regular expression grep regular expression](https://linuxhandbook.com/content/images/2020/07/regex.png)
Pipe character (|) in grep is used to specify that either of two whole subexpressions occur in a position. In this article, let us review some advanced regular expression with examples. The result is that the regex-directed engine will return the leftmost match. The regex will try all possible permutations of the regex, in exactly the same order.
![grep regular expression grep regular expression](https://www.cyberciti.biz/media/new/faq/2010/02/Linux-and-Unix-Regular-Expressions-In-grep.png)
Only if all possibilities have been tried and found to fail, will the regex engine continue with the second character in the text. It will try all possible permutations of the regular expression at the first character. When applying a regex to a string, the regex engine will start at the first character of the string. You can often accomplish complex tasks with a single regular expression instead of writing several lines of codes. In our previous regular expression part 1 article, we reviewed basic reg-ex with practical examples.īut we can do much more with the regular expressions.