Grep log and get text between log delimiters

Question

Is there a way to grep a log and find text between the log entry delimeters? Our log file separates the line entry with characters "-------" So when I search the text word I want all the lines before and after the delimeters in the log.

Sample log

------------------------------------------------------------------------
 r132279 | USERID | 2014年04月30日 12:59:09 -0700 (2014年4月30日) | 3 lines
 Removed unused "Calculated Fields" column entry.
 Jira ID: JIRA-977
------------------------------------------------------------------------

In the above i would Grep the word Fields but want all the lines between the "----" lines

Answer 1

If you know how big the record is, then you can output additional lines of context before (-B) and after (-A) the matching line e.g.

grep -A2 -B2 'Fields' sample.log

or for context both before and after the match line

grep -C3 'Fields' sample.log

As far as I know, the only way to do a true multiline match (rather than a single line match plus context) in GNU grep is by using the PCRE regex mode (-P) with the -z flag to prevent breaking on newlines. For example, you could try

grep -zPo '(\n-+\n)\K(.|\n)+?Fields(.|\n)+?(?=\n-+\n)'

which does a non-greedy match of the string Fields surrounded by any characters OR newlines, provided it is bookended by the newline-hyphens-newline delimiters. An equivalent expression in pcregrep is

pcregrep -Mo '(\n-+\n)\K(.|\n)+?Fields(.|\n)+?(?=\n-+\n)'

Another option for this kind of record-structured data is awk: in particular, GNU awk allows a regular expression to be used for the internal record separator RS e.g.

$ gawk -vRS='\n-+\n' '/Fields/ {print}' sample.log
r132279 | USERID | 2014年04月30日 12:59:09 -0700 (2014年4月30日) | 3 lines
Removed unused "Calculated Fields" column entry.
Jira ID: JIRA-977

• user3609755: gawk worked well . But when there is no DESCRIPTION field it outputs all lines. Thanks

Answer 2

A Perl solution similar to the gawk one in steeldriver's answer in case gawk isn't available:

perl -ne 'BEGIN{$/= "-"x72 . "\n"} chomp and print if /Fields/' log_file

Replace 72 by the actual number of dashes in your delimiter.

• steeldriver: Nice! I must make an effort to learn some perl - I was trying to figure out a way to do a multiline match with grep -zP but couldn't
• Joseph R.: @steeldriver I have seen people around here refer to a tool called pcregrep that is capable of doing multiline greps.
• steeldriver: Thanks, I have added tentative grep -zP and pcregrep solutions - feel free to improve them since I only know just about enough perl to be dangerous!