Regex (grep) for multi-line search needed [duplicate]

by

Without the need to install the grep variant pcregrep, you can do a 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 Treat the input as a set of lines, each terminated by a zero byte (the ASCII NUL character) instead of a newline. That is, grep knows where the ends of the lines are, but sees the input as one big line. Beware this also adds a trailing NUL char if used with -o, see comments.

-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.

More Related Contents:

  1. How to invert a grep expression
  2. How to make “grep” read patterns from a file?
  3. How to extract all Yahoo emails from a .CSV file?
  4. How to find patterns across multiple lines using grep?
  5. Validating IPv4 addresses with regexp
  6. How do I grep for all non-ASCII characters?
  7. How to use regex with find command?
  8. Negative matching using grep (match lines that do not contain foo)
  9. (grep) Regex to match non-ASCII characters?
  10. Insert contents of a file after specific pattern match
  11. Regex lookahead for ‘not followed by’ in grep
  12. Using the star sign in grep
  13. Why doesn’t `\d` work in regular expressions in sed? [duplicate]
  14. How do you extract IP addresses from files using a regex in a linux shell?
  15. Bash, grep between two lines with specified string
  16. sed join lines together
  17. What’s wrong with my lookahead regex in GNU sed?
  18. What does ‘\K’ mean in this regex?
  19. Unix grep regex containing ‘x’ but not containing ‘y’
  20. Does lookbehind work in sed?
  21. Difference between egrep and grep
  22. Recursively change file extensions in Bash
  23. Using sed and grep/egrep to search and replace
  24. Grep and regex – why am I escaping curly braces?
  25. How to do a non-greedy match in grep?
  26. grep regex whitespace behavior
  27. Whats the difference between sed -E and sed -e
  28. Regex for time in hh:mm am/pm format
  29. Grammatical inference of regular expressions for given finite list of representative strings?
  30. Regex empty string or email

Leave a Comment