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Operating Systems Solaris grep and display few lines before and after Post 302098992 by Ygor on Thursday 7th of December 2006 07:38:57 PM
Old 12-07-2006
Try...
Code:
nawk 'c-->0;$0~s{if(b)for(c=b+1;c>1;c--)print r[(NR-c+1)%b];print;c=a}b{r[NR%b]=$0}' b=2 a=4 s="string" file1

...where "b" and "a" are the number of lines to print before and after string "s".

---edit----

It's not the best generic solution because it can't handle the case if the search string is repeated in the "before" lines.

A better way...
Code:
nawk '$0~s{for(c=NR-b;c<=NR+a;c++)r[c]=1}{q[NR]=$0}END{for(c=1;c<=NR;c++)if(r[c])print q[c]}' b=2 a=4 s="string" file1

...where "b" and "a" are the number of lines to print before and after string "s".

Last edited by Ygor; 05-31-2012 at 08:51 AM.. Reason: Had to update this post because my buggy code is propagating all over the internet.
These 6 Users Gave Thanks to Ygor For This Post:
 

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STAG-GREP(1p)						User Contributed Perl Documentation					     STAG-GREP(1p)

NAME
stag-grep - filters a stag file (xml, itext, sxpr) for nodes of interest SYNOPSIS
stag-grep person -q name=fred file1.xml stag-grep person 'sub {shift->get_name =~ /^A*/}' file1.xml stag-grep -p My::Foo -w sxpr record 'sub{..}' file2 USAGE
stag-grep [-p|parser PARSER] [-w|writer WRITER] NODE -q tag=val FILE stag-grep [-p|parser PARSER] [-w|writer WRITER] NODE SUB FILE stag-grep [-p|parser PARSER] [-w|writer WRITER] NODE -f PERLFILE FILE DESCRIPTION
parsers an input file using the specified parser (which may be a built in stag parser, such as xml) and filters the resulting stag tree according to a user-supplied subroutine, writing out only the nodes/elements that pass the test. the parser is event based, so it should be able to handle large files (although if the node you parse is large, it will take up more memory) ARGUMENTS
-p|parser FORMAT FORMAT is one of xml, sxpr or itext, or the name of a perl module xml assumed as default -w|writer FORMAT FORMAT is one of xml, sxpr or itext, or the name of a perl module -c|count prints the number of nodes that pass the test -filterfile|f a file containing a perl subroutine (in place of the SUB argument) -q|query TAG1=VAL1 -q|query TAG2=VAL2 ... -q|query TAGN=VALN filters based on the field TAG other operators can be used too - eg <, <=, etc multiple q arguments can be passed in for more complex operations, pass in your own subroutine, see below SUB a perl subroutine. this subroutine is evaluated evry time NODE is encountered - the stag object for NODE is passed into the subroutine. if the subroutine passes, the node will be passed to the writer for display NODE the name of the node/element we are filtering on FILE the file to be parser. If no parser option is supplied, this is assumed to a be a stag compatible syntax (xml, sxpr or itext); otherwise you should parse in a parser name or a parser module that throws stag events SEE ALSO
Data::Stag perl v5.10.0 2008-12-23 STAG-GREP(1p)
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