How to search for multiple strings in a log file using less command in unix?

Question

I want to search for multiple strings in a log file. Only those entries should be highligted where all the search strings are there in same line. Can i use less command for this or any other better option. My log file size is typically few GBs.

Vincenz

Answer 1

When you want to search for string1 or string2, use /string1|string2. You said you wanted lines where you find both:

/string1.*string2

When you do not know the order in the line and want to see the complete line, you will need

/.*string1.*string2.*|.*string2.*string1.*

Or shorter

/.*(string1.*string2|string2.*string1).*

Combining more words without a fixed order will become a mess, and filtering first with awk is nice.

Edgell

Thanks! It worked for me. I personally prefer less over awk because of "if file is open i can quickly change the search string, search forward/backward from the current location." Ability to search for multiple strings with less is a bonus. – Vincenz

You prefer it because this answer just tackles two search patterns. This get's super complicated when you increase the number of patterns or the patterns are more complex. three patterns are almost impossible to type. – Commission

@Commission agree, in my case order of search strings is known and i have just 2 or 3 search strings max, so its preferred. Otherwise like you suggested awk with less is the way to go. – Vincenz

Answer 2

Use awk to filter the file and less to view the filtered result:

awk '/pattern1/ && /pattern2/ && /pattern3/' file.log | less

If the file is big you may want to use stdbuf to see results earlier in less:

stdbuf awk '/pattern1/ && /pattern2/ && /pattern3/' file.log | less

Commission