Question

The problem is the following:
I have a document called brain.txt with lines of characters like this:

++++++++++[>++++++++>++++++>+<<<-]>+++.>+++++.<-.+.>>. word

The word at the end can really be any word.
How can i filter the lines from the document where every 7th character is a plus?
example: +......+......+......+..... word

I wrote the following command:

egrep '^\+(.{6}\+)+.{,6}\s' brain.txt

But it does not seem to work, can anyone explain me what is incorrect about this command please?

Answer 1

The problem is the shorthand notation {,6} which does not seem to work with the given regex flavor. Simply write it out:

egrep '^\+(.{6}\+)+.{0,6}\s' brain.txt

Note that this requires at least 2 +s. The single \+ at the beginning, and another one in the subpattern (because it is repeated at least once). If +.... word would be a valid line for you, use:

egrep '^\+(.{6}\+)*.{0,6}\s' brain.txt