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Gawk Find Pattern Print Lines Before and After

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# 1  
Old 10-31-2013
Gawk Find Pattern Print Lines Before and After
Using grep I can easily use:

Code:
cvs log |grep -iB 10 -A 10 'date: 2013-10-30'

to display search results and 10 lines before and after. How can this be accompished using gawk?
# 2  
Old 10-31-2013
Use an indexed array to store the lines before search pattern and print when pattern is matched.

Something like this should work:
Code:
cvs log | gawk -v L=10 '
        !/date: 2013-10-30/ {

                A[++c] = $0
        }
        /date: 2013-10-30/ {
                for ( i = (c - (L-1)); i <= c; i++ )
                        print A[i]
                print
                for ( j = 1; j <= L; j++ )
                {
                        getline
                        print
                }
                delete A
                c = 0
        }
'

Last edited by Yoda; 10-31-2013 at 07:15 PM.. Reason: delete array
# 3  
Old 10-31-2013
Try:
Code:
gawk 'c-->0; {p=p RS $0}; $0~s{print p; c=A} NR>=B{sub(/[^\n]*\n/,x,p)}' IGNORECASE=1 A=10 B=10 s='date: 2013-10-30' file


--
IGNORECASE is used because the OP's example was using the -i option and is looking for a GNU awk example...
Last edited by Scrutinizer; 10-31-2013 at 11:38 PM.. Reason: Corrected A and B, thanks RudiC
# 4  
Old 10-31-2013
As has been proposed many many times before: use a circular buffer, e.g.
Code:
awk     '               {T[NR%(B+1)]=$0}
         $0~s           {for (i=NR+1; i<=NR+B; i++) print T[i%(B+1)]
                         L=NR+A+1}
         NR<L
        ' A=10 B=10 s='date: 2013-10-30' file

@Scrutinizer: Nice and curt! But I think you mixed grep's A(fter) and B(efore), and you implied that RS equals \n.
This User Gave Thanks to RudiC For This Post:
Scrutinizer
# 5  
Old 10-31-2013
Thanks, yes I reversed the meaning of "A" and "B" , corrected it in my post. Yes RS always equals "\n" in this case because this is meant to imitate grep's behavior, where this is always the case..
Last edited by Scrutinizer; 10-31-2013 at 11:39 PM..
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