I wanted to put a time stamp in a log file whenever a script on a Linux system is run. If you just enter
date with no parameters at
a shell prompt, you will see something like the following:$ date Sun Jun 21 16:10:49 EDT 2015
But you can modify how the output from the date command is presented by
specifying command line parameters for the command using
date +format, where format is how you wish the
output formatted. Parameters that can be used to format the display are listed
below:
| 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) |
Table from HowTo Format Date For Display or Use In a Shell Script by Vivek Gite on February 27, 2007
E.g., if I wanted to display the date in the form of year-month-day, I could use the following:
$ date +"%y-%m-%d" 15-06-21
If you use a lowercase "y", then the year will be displayed as a two-digit year, i.e. "15" in this case for 2015, but if I wanted to have the year displayed as a four-digit year, I could use an uppercase "Y" as shown below:
$ date +"%Y-%m-%d" 2015-06-21
In this case I also wanted to log the time in 24-hour format, aka
"military time", on the same line as the date, so I could append a
%T.
$ date +"%Y-%m-%d %T" 2015-06-21 16:31:40
If I wanted to store the results of the command in a variable, I could use the following:
$ NOW=$(date +"%Y-%m-%d %T") $ echo $NOW 2015-06-21 16:48:15
