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?
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(.|
)*
end" file
begin
Some text goes here.
end
note: for other commands just replace the '^' & '$' anchors with new-line anchor '
'
______________________________
With grep command:
grep -Pzo "^begin$(.|
)*^end$" file
If you want don't include the patterns "begin" and "end" in result, use grep with Lookbehind and Lookahead support.
grep -Pzo "(?<=^begin$
)(.|
)*(?=
^end$)" file
Also you can use K notify instead of Lookbehind assertion.
grep -Pzo "^begin$
K(.|
)*(?=
^end$)" file
K option ignore everything before pattern matching and ignore pattern itself.
Or as @AvinashRaj suggests there are simple easy grep as following:
grep -Pzo "(?s)^begin$.*?^end$" file
grep -Pzo "^begin$[sS]*?^end$" file
(?s) tells grep to allow the dot to match newline characters.
[sS] matches any character that is either whitespace or non-whitespace.
And their output without including "begin" and "end" is as following:
grep -Pzo "^begin$
K[sS]*?(?=
^end$)" file # or grep -Pzo "(?<=^begin$
)[sS]*?(?=
^end$)"
grep -Pzo "(?s)(?<=^begin$
).*?(?=
^end$)" file
see the full test of all commands here (out of dated as grep behavior with -P parameter is changed)
^ 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.
-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.
