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Top Forums Shell Programming and Scripting Grep pattern only and surrounding lines Post 302978032 by jacobs.smith on Monday 25th of July 2016 01:12:20 PM
Old 07-25-2016
Grep pattern only and surrounding lines

Hello,

I am trying to grep search a pattern and a line before it.

Code:
cat input
>record1
hello1hello2hellonhello3
>record2
helloohello1hello2hello3

When I use, grep with -o option and either of -A/B/C options, I still can't see lines before or after the pattern. But the exact pattern is being printed fine though. Any pointers are appreciated.

Expected output is

Code:
cat input | grep -o "hello[a-z]hello"
>record1
hellonhello
>record2
helloohello

But current output is

Code:
cat input | grep -o -B 1 "hello[a-z]hello"
hellonhello
helloohello


Thanks in advance.
 

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GREP(1) 						      General Commands Manual							   GREP(1)

NAME
grep - search a file for lines containing a given pattern SYNOPSIS
grep [-elnsv] pattern [file] ... OPTIONS
-e -e pattern is the same as pattern -c Print a count of lines matched -i Ignore case -l Print file names, no lines -n Print line numbers -s Status only, no printed output -v Select lines that do not match EXAMPLES
grep mouse file # Find lines in file containing mouse grep [0-9] file # Print lines containing a digit DESCRIPTION
Grep searches one or more files (by default, stdin) and selects out all the lines that match the pattern. All the regular expressions accepted by ed and mined are allowed. In addition, + can be used instead of * to mean 1 or more occurrences, ? can be used to mean 0 or 1 occurrences, and | can be used between two regular expressions to mean either one of them. Parentheses can be used for grouping. If a match is found, exit status 0 is returned. If no match is found, exit status 1 is returned. If an error is detected, exit status 2 is returned. SEE ALSO
cgrep(1), fgrep(1), sed(1), awk(9). GREP(1)
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