I know this is a very simple question and discussed many times, but I can’t understand where I am doing mistake in my command.
I would like to replace the lines which starts with “It” as 99999. Each row starts with several blank spaces.
infile.txt 3 2 3 4 It is not a number = /home/kayan/data 3 5 It is not a number = /home/kayan/data 4 5
sed -i 's/^I/99999/g' infile.txt
But it not working.