Insert String every n lines, resetting line counter at desired string


 
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# 1  
Old 03-17-2015
Hammer & Screwdriver Insert String every n lines, resetting line counter at desired string

I need to read a text file and insert a string every n lines, but also have the line counter restart when I come across a header string.

Line repeating working every 3 lines using code:

Code:
sed '0~3 s/$/\nINSERT/g' < INPUT/PATH/FILE_NAME.txt > OUTPUT/PATH/FILE_NAME.txt

I cannot seem to find how to restart counter when line=Header... I have also tried using a shell command with much less success.

ex. input:
Header Line Here
dog
cat
fish
pony
horse
Header Line Here
whale
Header Line Here
shark
lizard
dolphin


required output:
Header Line Here
dog
cat
INSERT
fish
pony
horse
INSERT
bird
Header Line Here
whale
Header Line Here
shark
lizard
INSERT
dolphin

Last edited by Skonectthedots; 03-17-2015 at 10:11 AM.. Reason: Editing code
# 2  
Old 03-17-2015
sed does not have variables and cannot count.
With awk it's simple:
Code:
awk '(++n==3) {print "INSERT"; n=0} (/Header/) {n=0} {print}' file

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