Learn how to format date and time to use in a shell script or as a variable along with different format examples.
There are many times you need to use date in your shell script e.g. to name log file, to pass it as a variable, etc. So we need a different format of dates that can be used as a string or variable in our scripts. In this article, let’s see how to use date in shell script and what all different types of formats you can use.
- Check timedatectl command to easily manage date & time in Linux
How to use date in shell script?
You can use the date by inserting shell execution within the command. For example, if you want to create a log file by inserting the current date in it, you can do it by following way –
root@kerneltalks # echo test > /tmp/`date +%d`.txt root@kerneltalks # ls -lrt -rw-r--r--. 1 root root 5 Sep 10 09:10 10.txt
Basically you need to pass format identifier with
+% to date command to get your desired format of the output. There is a different identifier date command supply.
You can even save specific date format to some variable like –
root@kerneltalks # MYDATE=`date +%d.%b.%Y` root@kerneltalks # echo $MYDATE 10.Sep.2018
Different format variables for date command
These format identifiers are from date command
man page :
%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., 20) %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 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 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 alphabetic time zone abbreviation (e.g., EDT)
Using combinations of above you can get your desired date format as output to use in shell script! You can even use
%n for new-line and
%t for adding a tab in outputs that are mostly not needed since you will be using it as a single string.
Different date format examples
For your convenience and ready to use, I listed below combinations for different date formats.
root@kerneltalks # date +%d_%b_%Y 10_Sep_2018 root@kerneltalks # date +%D 09/10/18 root@kerneltalks # date +%F-%T 2018-09-10-11:09:51 root@kerneltalks # echo today is `date +%A` today is Monday root@kerneltalks # echo Its `date +%d` of `date +%B" "%Y` and time is `date +%r` Its 10 of September 2018 and time is 11:13:42 AM