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Append variable to only certain lines


 
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# 1  
Old 06-24-2009
Append variable to only certain lines

Hi There!
I'm trying to write a shell script which generates a random hexadecimal number and then appends it to the end of lines XX onwards of a certain file. XX is determined by a certain string on the previous line.

Thus for example, if the input file is
Quote:
This is line 1
This is line 2
This is line 3
SEPARATOR
This is line 4
This is line 5
I search for the string "SEPARATOR" and starting with the next line, keep appending the hex strings. Thus, the output should be
Quote:
This is line 1
This is line 2
This is line 3
SEPARATOR
This is line 4 <RANDOM HEX>
This is line 5 <RANDOM HEX>
I can generate the random hex strings fine, and also find the line number to start appending from, but im having problems with the actual appending.

What is the best way to do this? (The input files could have 10k+ lines)

Thanks!
-orno
# 2  
Old 06-24-2009
Try this:

Code:
awk -v var="<RANDOM HEX>" '/SEPARATOR/{f=1;print;next}f{$0=$0 FS var}1' file

# 3  
Old 06-24-2009
That's perfect

What if I want to append the variable ONLY on the the line 2 lines after the line found with the string SEPARATOR?

i.e. Output should be
Quote:
This is line 1
This is line 2
This is line 3
SEPARATOR
This is line 4
This is line 5 <RANDOM HEX>
This is line 6
# 4  
Old 06-24-2009
Quote:
Originally Posted by orno
That's perfect

What if I want to append the variable ONLY on the the line 2 lines after the line found with the string SEPARATOR?

i.e. Output should be
Should be something like:

Code:
 awk -v var="<RANDOM HEX>" '/SEPARATOR/{print;getline;print;getline;$0=$0 FS var}1' file


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