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2013.04.20 13:46

Most common Bash date commands for timestamping

Filed under: Computing — Tags: , , , , — zxq9 @ 13:46

From time to time I get asked how to use the date command to generate a timestamp. Here is an idiot-friendly script you can post for reference in your team’s bin/ if you get interrupted about timestamp questions or have an aversion to typing phrases like “man date” (with or without a space).

All but the first one and last three produce filename-friendly strings.

A big thanks to the following folks for pointing out mistakes and suggesting useful format inclusions:

  • 2013-05: Rich for the reminder to include UTC and timezoned stamps.
  • 2017-10: “Hamilton and Meg” (haha!) for pointing out I had my 4 year example formats messed up and for prodding me to include a 2-year example.
  • 2018-01: Autumn Gray for suggesting that I add examples of including short and long days of the week.
#! /bin/bash

# An overly obvious reference for most commonly requested bash timestamps
# Now all you Mac fags can stop pestering me.

cat << EOD
        Format/result           |       Command              |          Output
YYYY-MM-DD_hh:mm:ss             | date +%F_%T                | $(date +%F_%T)
YYYYMMDD_hhmmss                 | date +%Y%m%d_%H%M%S        | $(date +%Y%m%d_%H%M%S)
YYYYMMDD_hhmmss (UTC version)   | date --utc +%Y%m%d_%H%M%SZ | $(date --utc +%Y%m%d_%H%M%SZ)
YYYYMMDD_hhmmss (with local TZ) | date +%Y%m%d_%H%M%S%Z      | $(date +%Y%m%d_%H%M%S%Z)
YYYYMMSShhmmss                  | date +%Y%m%d%H%M%S         | $(date +%Y%m%d%H%M%S)
YYYYMMSShhmmssnnnnnnnnn         | date +%Y%m%d%H%M%S%N       | $(date +%Y%m%d%H%M%S%N)
YYMMDD_hhmmss                   | date +%y%m%d_%H%M%S        | $(date +%y%m%d_%H%M%S)
Seconds since UNIX epoch:       | date +%s                   | $(date +%s)
Nanoseconds only:               | date +%N                   | $(date +%N)
Nanoseconds since UNIX epoch:   | date +%s%N                 | $(date +%s%N)
ISO8601 UTC timestamp           | date --utc +%FT%TZ         | $(date --utc +%FT%TZ)
ISO8601 UTC timestamp + ms      | date --utc +%FT%T.%3NZ     | $(date --utc +%FT%T.%3NZ)
ISO8601 Local TZ timestamp      | date +%FT%T%Z              | $(date +%FT%T%Z)
YYYY-MM-DD (Short day)          | date +%F\(%a\)             | $(date +%F\(%a\))
YYYY-MM-DD (Long day)           | date +%F\(%A\)             | $(date +%F\(%A\))

If executed, it will produce the (obvious) output:

        Format/result           |       Command              |          Output
YYYY-MM-DD_hh:mm:ss             | date +%F_%T                | 2018-01-24_13:06:51
YYYYMMDD_hhmmss                 | date +%Y%m%d_%H%M%S        | 20180124_130651
YYYYMMDD_hhmmss (UTC version)   | date --utc +%Y%m%d_%H%M%SZ | 20180124_040651Z
YYYYMMDD_hhmmss (with local TZ) | date +%Y%m%d_%H%M%S%Z      | 20180124_130651JST
YYYYMMSShhmmss                  | date +%Y%m%d%H%M%S         | 20180124130651
YYYYMMSShhmmssnnnnnnnnn         | date +%Y%m%d%H%M%S%N       | 20180124130651170243401
YYMMDD_hhmmss                   | date +%y%m%d_%H%M%S        | 180124_130651
Seconds since UNIX epoch:       | date +%s                   | 1516766811
Nanoseconds only:               | date +%N                   | 174236092
Nanoseconds since UNIX epoch:   | date +%s%N                 | 1516766811175655627
ISO8601 UTC timestamp           | date --utc +%FT%TZ         | 2018-01-24T04:06:51Z
ISO8601 UTC timestamp + ms      | date --utc +%FT%T.%3NZ     | 2018-01-24T04:06:51.178Z
ISO8601 Local TZ timestamp      | date +%FT%T%Z              | 2018-01-24T13:06:51JST
YYYY-MM-DD (Short day)          | date +%F\(%a\)             | 2018-01-24(æ°´)
YYYY-MM-DD (Long day)           | date +%F\(%A\)             | 2018-01-24(水曜日)

Note that the last two, short and long day-of-week are dependent on the environment variable LANG. After setting LANG=en_US we wind up with the following:

YYYY-MM-DD (Short day)          | date +%F\(%a\)             | 2018-01-24(Wed)
YYYY-MM-DD (Long day)           | date +%F\(%A\)             | 2018-01-24(Wednesday)

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