HowTo Format Date For Display or Use In a Shell Script

You need to use the standard date command to format date or time. You can use the same command with the shell script.

Syntax

The syntax is

date +FORMAT

OR

date +"%FORMAT"

OR

date +"%FORMAT%FORMAT"

OR

date +"%FORMAT-%FORMAT"

Task: Display date in mm-dd-yy format

Open a terminal and type the following date command:
$ date +"%m-%d-%y"
Sample output:

02-27-07

To turn on 4 digit year display:
$ date +"%m-%d-%Y"
Just display date as mm/dd/yy format:
$ date +"%D"

Task: Display time only

Type the following command:
$ date +"%T"
Outputs:

19:55:04

To display locale's 12-hour clock time, enter:
$ date +"%r"
Outputs:

07:56:05 PM

To display time in HH:MM format, type:
$ date +"%H-%M"
Sample outputs:

00-50

How do I save time/date format to the shell variable?

Simply type the following command at the shell prompt:
$ NOW=$(date +"%m-%d-%Y")
To display a variable use echo / printf command:
$ echo $NOW

A sample shell script

#!/bin/bash

NOW=$(date +"%m-%d-%Y")

FILE="backup.$NOW.tar.gz"

echo "Backing up data to /nas42/backup.$NOW.tar.gz file, please wait..."

# rest of script

# tar xcvf /nas42/backup.$NOW.tar.gz /home/ /etc/ /var

A complete list of FORMAT control characters supported by the date command

FORMAT controls the output. It can be the combination of any one of the following:

%FORMAT String	Description
%%	a literal %
%a	locale's abbreviated weekday name (e.g., Sun)
%A	locale's full weekday name (e.g., Sunday)
%b	locale's abbreviated month name (e.g., Jan)
%B	locale's full month name (e.g., January)
%c	locale's date and time (e.g., Thu Mar 3 23:05:25 2005)
%C	century; like %Y, except omit last two digits (e.g., 21)
%d	day of month (e.g, 01)
%D	date; same as %m/%d/%y
%e	day of month, space padded; same as %_d
%F	full date; same as %Y-%m-%d
%g	last two digits of year of ISO week number (see %G)
%G	year of ISO week number (see %V); normally useful only with %V
%h	same as %b
%H	hour (00..23)
%I	hour (01..12)
%j	day of year (001..366)
%k	hour ( 0..23)
%l	hour ( 1..12)
%m	month (01..12)
%M	minute (00..59)
%n	a newline
%N	nanoseconds (000000000..999999999)
%p	locale's equivalent of either AM or PM; blank if not known
%P	like %p, but lower case
%r	locale's 12-hour clock time (e.g., 11:11:04 PM)
%R	24-hour hour and minute; same as %H:%M
%s	seconds since 1970-01-01 00:00:00 UTC
%S	second (00..60)
%t	a tab
%T	time; same as %H:%M:%S
%u	day of week (1..7); 1 is Monday
%U	week number of year, with Sunday as first day of week (00..53)
%V	ISO week number, with Monday as first day of week (01..53)
%w	day of week (0..6); 0 is Sunday
%W	week number of year, with Monday as first day of week (00..53)
%x	locale's date representation (e.g., 12/31/99)
%X	locale's time representation (e.g., 23:13:48)
%y	last two digits of year (00..99)
%Y	year
%z	+hhmm numeric timezone (e.g., -0400)
%:z	+hh:mm numeric timezone (e.g., -04:00)
%::z	+hh:mm:ss numeric time zone (e.g., -04:00:00)
%:::z	numeric time zone with : to necessary precision (e.g., -04, +05:30)
%Z	alphabetic time zone abbreviation (e.g., EDT)