How to derive current date and time and append at the end of each line that contains 'Hello'

Question

I have the following file party.txt that contains something like the following:

Hello Jacky
Hello Peter
Bye Johnson
Hello Willy
Bye Johnny
Hello Mar         


        

Answer 1

One way using awk:

awk -v date="$(date +"%Y-%m-%d %r")" '/Hello/ { print $0, date}' party.txt

Results:

Hello Jacky 2012-09-11 07:55:51 PM
Hello Peter 2012-09-11 07:55:51 PM
Hello Willy 2012-09-11 07:55:51 PM
Hello Mary 2012-09-11 07:55:51 PM
Hello Wendy 2012-09-11 07:55:51 PM

Note that the date value is only set when awk starts, so it will not change, even if the command takes a long time to run.