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Grep file and print value only if the following line doesnt contain value xxxx


 
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# 1  
Grep file and print value only if the following line doesnt contain value xxxx

Hi All,
I have some large files which I would like to obtain some data from, I want to grep (or alturnative method) out certain values hut only if the folowing line doesnt contain a certain value. I will explain better below showing an example print of the data.

Code:
NE : V0001
NE : V0002
NE : V0003
NE : V0004
ccc
NE : V00005
ccc
NE : V00006

from the above I want to print every line where NE : is present but only if the line under doesnt contain NE :

I'm sure one of you guys will be able to help.

Thanks again.
# 2  
Any attempts from your side?
# 3  
Quote:
Originally Posted by RudiC
Any attempts from your side?
Hi Rudi,
Its something I have never done and was struggling to find a solution, hopefully you or someone on here will be able to help me out.

Thanks in advance.
# 4  
Like so?
Code:
awk '/^NE :/ {P=$0; next} {print P}' file
NE : V0004
NE : V00005

This User Gave Thanks to RudiC For This Post:
# 5  
Quote:
Originally Posted by RudiC
Like so?
Code:
awk '/^NE :/ {P=$0; next} {print P}' file
NE : V0004
NE : V00005

Perfect, Thanks Rudi really apprecaite it. Would you mind explaining the command just to help me understand.

Thanks.
# 6  
The suggestions works if there is always one line without NE :. If there are more lines then P gets printed for every following line, so a provision would need to be made if that could be the case..

Also, technically from the description it follows that the last line should get printed since it does not have a line following it with NE :
This User Gave Thanks to Scrutinizer For This Post:
# 7  
awk reads and processes every single line in the input stream. A line starting with NE : is stored in the variable P, overwriting the last one, then that line's processing is abandoned and the next is read/processed. If it doesn't start with NE : P is printed, representing the last line.
BTW, I found a flaw in above: If there's multiple non-NE lines, P is printed several times. This should avoid it:
Code:
awk '/^NE :/ {P=$0; next} P {print P; P=""}' file
NE : V0004
NE : V00005

This User Gave Thanks to RudiC For This Post:
 

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