Format Date In a Shell Script

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 GNU/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)

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

The following works on Apple OS X, FreeBSD and BSD version of the date command:

%A is replaced by national representation of the full weekday name.
%a is replaced by national representation of the abbreviated weekday name.
%B is replaced by national representation of the full month name.
%b is replaced by national representation of the abbreviated month name.
%C is replaced by (year / 100) as decimal number; single digits are preceded by a zero.
%c is replaced by national representation of time and date.
%D is equivalent to “%m/%d/%y”.
%d is replaced by the day of the month as a decimal number (01-31).
%E* %O* POSIX locale extensions. The sequences %Ec %EC %Ex %EX %Ey %EY %Od %Oe %OH %OI %Om %OM %OS %Ou %OU %OV %Ow %OW %Oy are supposed to provide alternate representations.
Additionally %OB implemented to represent alternative months names (used standalone, without day mentioned).
%e is replaced by the day of the month as a decimal number (1-31); single digits are preceded by a blank.
%G is replaced by a year as a decimal number with century. This year is the one that contains the greater part of the week (Monday as the first day of the week).
%g is replaced by the same year as in “%G”, but as a decimal number without century (00-99).
%H is replaced by the hour (24-hour clock) as a decimal number (00-23).
%h the same as %b.
%I is replaced by the hour (12-hour clock) as a decimal number (01-12).
%j is replaced by the day of the year as a decimal number (001-366).
%k is replaced by the hour (24-hour clock) as a decimal number (0-23); single digits are preceded by a blank.
%l is replaced by the hour (12-hour clock) as a decimal number (1-12); single digits are preceded by a blank.
%M is replaced by the minute as a decimal number (00-59).
%m is replaced by the month as a decimal number (01-12).
%n is replaced by a newline.
%O* the same as %E*.
%p is replaced by national representation of either “ante meridiem” (a.m.) or “post meridiem” (p.m.) as appropriate.
%R is equivalent to “%H:%M”.
%r is equivalent to “%I:%M:%S %p”.
%S is replaced by the second as a decimal number (00-60).
%s is replaced by the number of seconds since the Epoch, UTC (see mktime(3)).
%T is equivalent to “%H:%M:%S”.
%t is replaced by a tab.
%U is replaced by the week number of the year (Sunday as the first day of the week) as a decimal number (00-53).
%u is replaced by the weekday (Monday as the first day of the week) as a decimal number (1-7).
%V is replaced by the week number of the year (Monday as the first day of the week) as a decimal number (01-53). If the week containing January 1 has four or more days in the new year, then it is week 1; otherwise it is the last week of the previous year, and the next week is week 1.
%v is equivalent to “%e-%b-%Y”.
%W is replaced by the week number of the year (Monday as the first day of the week) as a decimal number (00-53).
%w is replaced by the weekday (Sunday as the first day of the week) as a decimal number (0-6).
%X is replaced by national representation of the time.
%x is replaced by national representation of the date.
%Y is replaced by the year with century as a decimal number.
%y is replaced by the year without century as a decimal number (00-99).
%Z is replaced by the time zone name.
%z is replaced by the time zone offset from UTC; a leading plus sign stands for east of UTC, a minus sign for west of UTC, hours and minutes follow with two digits each and no delimiter between them (common form for RFC 822 date headers).
%+ is replaced by national representation of the date and time (the format is similar to that produced by date(1)).
%-* GNU libc extension. Do not do any padding when performing numerical outputs.
%_* GNU libc extension. Explicitly specify space for padding.
%0* GNU libc extension. Explicitly specify zero for padding.
%% is replaced by %.

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