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

If you're open to using Perl:

perl -MPOSIX -lne 'if (/Hello/){ print "$_ " . strftime "%Y-%m-%d",localtime }' party.txt

produces this output

Hello Jacky 2015-10-01
Hello Peter 2015-10-01
Hello Willy 2015-10-01
Hello Mary 2015-10-01
Hello Wendy 2015-10-01

Here's how it works:

• -n loops around every line of the input file, do not automatically print each line

• -l removes newlines before processing, and adds them back in afterwards

• -e execute the perl code

• $_ is the current line

• -MPOSIX loads the POSIX module, which includes strftime

• localtime and strftime prints the time, given the format %Y-%m-%d