How to insert string in a list?

How are you defining a "block" of text? Do you want to modify only every 3rd line? You might want to submit a sample file.

Hi Nils, Yes, here's an example. I'm trying to locate the word "Word1" for each block as such: Word1 AAAAAAAAAAAAAA { BBBBBBBBBBBBBB CCCCCCCCCCCCCC DDDDDDDDDDDDDD } Word1 BBBBBBBBBBBBB { ZZZZZZZZZZZZZ WWWWWWWWWWWWW QQQQQQQQQQQQ } Word12 AAAAAAAAAAAAA { BBBBBBBBBBBBB CCCCCCCCCCCCC DDDDDDDDDDDDD } I would like locate each block above by the word "Word1" and then insert a string of text (Ts) in the 4th line of each block as such: Word1 AAAAAAAAAAAAAA { BBBBBBBBBBBBBB CCCCCCCCCCCCCC DDDDDDDDDDDDDD TTTTTTTTTTTTTT } Word1 BBBBBBBBBBBBBB { ZZZZZZZZZZZZZZ WWWWWWWWWWWWWW QQQQQQQQQQQQQQ TTTTTTTTTTTTTT } Thanks for your help.

I'm trying to identify a pattern. Does 'Word1' always start at the beginning of the line in line 1 of the block? Can we search just for 'Word1' at the beginning of the line and not worry about whether it's the first line of the block?

Yes, the word "word1" starts at the beginning of each block (as a reference point). From the reference point one, a string is inserted on the 4th line within the "{ }". The reason for this is that there are other blocks that start with a "word" and a number, like word12, word45, wordxy, etc. I want to target a specific word, in this case "word1". Thanks.

Here's an awk script that prints the line of TTTs after the 4th line if the beginning of the line matches "Word1": #!/bin/ksh awk ' BEGIN { allt="TTTTTTTTTTTTTTTTT"; cnt=0; prn=0 } { if($0 ~ /^Word1/) prn=1 if(prn == 1) cnt++ printf("%s\n", $0) if(prn == 1 && cnt == 4) { prn=0 cnt=0 printf("%s\n", allt) } } ' datafile.txt > newdatafile.txt

Nils, It's perfect! Thanks a bunch....