I have a couple thousand files with the same line formatting. I am trying to replace the 17th character (a letter) in every line that begins with a string (the word "ATOM"), without changing anything else in the file. So for example, I'd like to replace the 17th character after the word ATOM from "D" to "A":
INPUT
ATOM 14632 2HG2 VAL D 923 56.949 47.137 72.598 1.00 0.00 H
OUTPUT
ATOM 14632 2HG2 VAL A 923 56.949 47.137 72.598 1.00 0.00 H
I'm using the following code, which changes the letter, but deletes everything before it in that line:
sed -i '.bak' 's/^\(ATOM.\{17\}\)D/\A/' input.file
OUTPUT
A 923 56.949 47.137 72.598 1.00 0.00 H
Any help on what I'm doing wrong here would be greatly appreciated.
The '.bak' is there since I'm on a Mac.
It's:
sed 's/^\(ATOM.\{16\}\)D/\1A/'
.\{16\} - You said I'd like to replace the 17th character after the word ATOM from "D" to "A". So you want to match any 16 characters and then match the 17th character that is a D.\1 - put what is remembered with the first \(...\) there.A - followed by an A.