How to use grep to print a match with a regular expression?

Question

linux

There is a binary file for two gigabytes (dump), you need to extract lines matching the pattern from it and save them to a text file. Tried
grep -P --regexp='PHPSESSID=(.+?);' dump.bin > result.txt
but as far as I understand, all the lines in which this regular expression occurs are written to the final file. I would like to get only what is contained in brackets.

Answer 1

You can add -o, then only parts of the lines that match the regular expression will be output.