Required 3 lines above the file and below file when string matches


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# 1  
Required 3 lines above the file and below file when string matches

i had requirement like i need to get "error" line of above 3 and below 3 from a file .I tried with the below script.But it's not working.

Code:
 
y='grep -n -i error /home/file.txt|cut -c1'
echo $y
head -$y /home/file.txt| tail -3 >tmp.txt
tail -$y /home/file.txt head -3 >>tmp.txt

# 2  
Check out the -B and -A options of grep.
# 3  
If
Code:
grep -A3 -B3 -i error /home/file.txt

doesn't work on your system, mayhap
Code:
tail -n +$(($(grep -ni error /home/file.txt | cut -d: -f1)-3)) /home/file.txt | head -7

does?
# 4  
If your grep doesn't support the -A and the -B options you can try:
Code:
awk 'NR==FNR{if($0 ~ /error/){n=NR}next}FNR > n-4 && FNR < n+4' /home/file.txt /home/file.txt


Last edited by Franklin52; 08-11-2015 at 09:04 AM..
These 2 Users Gave Thanks to Franklin52 For This Post:
# 5  
Thanks to all for your suggestions and Franklin52 code worked for me...
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If variable i has the value 10, after x = 5 + (++i); the value of x after this code is 15.
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