Clojure: what's the way to have current time string with babashka with least dependency?

Question

With the following expression,

bb '(new java.util.Date)'
#inst "2020-07-18T14:35:16.663-00:00"

I want to get a string, and slightly formatted as:

"2020-07-18 UTC 14:35:16"

With Babashka (bb), I wish to have the least dependency. Otherwise, I could use clj-time, etc. to achieve the goal.

Or if I should just use the OS's date utility instead, given I'm writing a script?

Answer 1

In babashka you can use the java.time package:

(import 'java.time.format.DateTimeFormatter
        'java.time.LocalDateTime)

(def date (LocalDateTime/now))
(def formatter (DateTimeFormatter/ofPattern "yyyy-MM-dd HH:mm:ss"))
(.format date formatter) ;;=> "2020-07-18 18:04:04"

Answer 2

For shell scripting purposes, I define my own convenience bash/zsh functions:

      function iso-date() {
        date "+%Y-%m-%d"
      }
      function iso-date-short() {
        date "+%Y%m%d"
      }
      function iso-time() {
        date "+%H:%M:%S"
      }
      function iso-time-short() {
        date "+%H%M%S"
      }
      function iso-date-time() {
        echo "$(iso-date)t$(iso-time)"
      }
      function iso-date-time-nice() {
        echo "$(iso-date) $(iso-time)"
      }
      function iso-date-time-str() {
        echo "$(iso-date-short)-$(iso-time-short)"
      }

with results:

    ~/cool > iso-date
    2020-07-18

    ~/cool > iso-date-short
    20200718

    ~/cool > iso-time      
    13:40:50

    ~/cool > iso-time-short
    134059

    ~/cool > iso-date-time
    2020-07-18t13:41:05

    ~/cool > iso-date-time-nice
    2020-07-18 13:41:10

    ~/cool > iso-date-time-str 
    20200718-134114

While I really like Babashka (and GraalVM in general!) the extra install step is overkill for simple stuff.

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See this repo for general GraalVM demo & Clojure template project, and then you can "roll your own" whenever you want!