linux - Regex (grep) for multi-line search needed

Question

This question already has answers here:

Answer 1

Without the need to install the grep variant pcregrep, you can do multiline search with grep.

$ grep -Pzo "(?s)^(s*)N*main.*?{.*?^1}" *.c

Explanation:

-P activate perl-regexp for grep (a powerful extension of regular expressions)

-z suppress newline at the end of line, substituting it for null character. That is, grep knows where end of line is, but sees the input as one big line.

-o print only matching. Because we're using -z, the whole file is like a single big line, so if there is a match, the entire file would be printed; this way it won't do that.

In regexp:

(?s) activate PCRE_DOTALL, which means that . finds any character or newline

N find anything except newline, even with PCRE_DOTALL activated

.*? find . in non-greedy mode, that is, stops as soon as possible.

^ find start of line

1 backreference to the first group (s*). This is a try to find the same indentation of method.

As you can imagine, this search prints the main method in a C (*.c) source file.