How Do I Grep for Multiple Patterns on Multiple Lines?
To Be Precise Some Text Begin Some Text Goes Here. End Some More Text and I Want to Extract Entire Block That Starts from "Begin" Till "End". with Awk We Can...
To be precise
Some text
begin
Some text goes here.
end
Some more text
and I want to extract entire block that starts from "begin" till "end".
with awk we can do like awk '/begin/,/end/' text.
How to do with grep?
2 Answers
Updated 18-Nov-2016 (since grep behavior is changed: grep with -P parameter now doesn't support ^ and $ anchors [on Ubuntu 16.04 with kernel v:4.4.0-21-generic])(wrong (non-)fix)
$ grep -Pzo "begin(.|\n)*\nend" file
begin
Some text goes here.
end
note: for other commands just replace the '^' & '$' anchors with new-line anchor '\n'
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With grep command:
grep -Pzo "^begin\$(.|\n)*^end$" file
If you want don't include the patterns "begin" and "end" in result, use grep with Lookbehind and Lookahead support.
grep -Pzo "(?<=^begin$\n)(.|\n)*(?=\n^end$)" file
Also you can use \K notify instead of Lookbehind assertion.
grep -Pzo "^begin$\n\K(.|\n)*(?=\n^end$)" file
\K option ignore everything before pattern matching and ignore pattern itself.
\n used for avoid printing empty lines from output.
Or as @AvinashRaj suggests there are simple easy grep as following:
grep -Pzo "(?s)^begin$.*?^end$" file
grep -Pzo "^begin\$[\s\S]*?^end$" file
(?s) tells grep to allow the dot to match newline characters.
[\s\S] matches any character that is either whitespace or non-whitespace.
And their output without including "begin" and "end" is as following:
grep -Pzo "^begin$\n\K[\s\S]*?(?=\n^end$)" file # or grep -Pzo "(?<=^begin$\n)[\s\S]*?(?=\n^end$)"
grep -Pzo "(?s)(?<=^begin$\n).*?(?=\n^end$)" file
see the full test of all commands here (out of dated as grep behavior with -P parameter is changed)
Note:
^ point the beginning of a line and $ point the end of a line. these added to the around of "begin" and "end" to matching them if they are alone in a line.
In two commands I escaped $ because it also using for "Command Substitution"($(command)) that allows the output of a command to replace the command name.
From man grep:
-o, --only-matching
Print only the matched (non-empty) parts of a matching line,
with each such part on a separate output line.
-P, --perl-regexp
Interpret PATTERN as a Perl compatible regular expression (PCRE)
-z, --null-data
Treat the input as a set of lines, each terminated by a zero byte (the ASCII
NUL character) instead of a newline. Like the -Z or --null option, this option
can be used with commands like sort -z to process arbitrary file names.
In case your grep doesn't support perl syntax (-P), you can try joining the lines, matching the pattern, then expanding the lines again as below:
$ tr '\n' , < foo.txt | grep -o "begin.*end" | tr , '\n'
begin
Some text goes here.
end
Sarah Jenkins is a veteran tech journalist with over 12 years of experience covering artificial intelligence, mobile innovations, and digital ethics. Her insights have appeared in leading technology publications worldwide.
