[DATE][AWK] Working with date and time is a common task for ev | LinuxCheatSheet

[DATE][AWK] Working with date and time is a common task for everyone.
There are different tools to do it with Linux, most common one is date

~]$ date -d "2018/01/17 20:01:37" +%s
1516215697
~]$ date -d @1516215697 +"%Y/%m/%d %H:%M:%S"
2018/01/17 20:01:37
~]$

You can format date output as you need using + option followed by date format specifier (man date). The -d option allow you to see the date you specify, not the current system time. Please note that -d support relative dates, like
~]$ echo -n "Now: "; date
Now: Thu Jan 18 13:38:45 CET 2018
~]$ echo -n "Yesterday: "; date -d "1 day ago"
Yesterday: Wed Jan 17 13:39:07 CET 2018
~]$ echo -n "Future: "; date -d "+ 3 weeks"
Future: Thu Feb 8 13:39:38 CET 2018
~]$

This can be useful in different ways when scripting, usually when you want to obtain a time range relative to the current time to perform some action.
Another way to manipulate date and time is through AWK. Have a look to mktime and strftime.
~]$ echo | awk '{print mktime("2018 01 17 20 01 37")}'
1516215697
~]$ echo | awk '{print strftime("%Y/%m/%d %H:%M:%S",1516215697)}'
2018/01/17 20:01:37
~]$

Last but not least, you can even mix awk and date command. This is useful for example when you have a log with date in a certain format and you want to transform it to another one for any reason (i.e. sorting, or extracting a time range). This is the base syntax to use date inside awk:
~]$ echo | awk '{"date" | getline d; print d}'
Wed Jan 17 21:59:12 CET 2018
~]$

Have a look at this example of transformation of apache common log format.

I hope you like it! Please vote for the channel or share it
https://tchannels.me/c/linuxcheatsheet
http://www.telegramitalia.it/linuxcheatsheet/

Bye
G.