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A sprinkle of Clojure for the command line.


$ bash <(curl -s
$ bb '(vec (dedupe *in*))' <<< '[1 1 1 1 2]'
[1 2]


If you're a bash expert, you probably don't need this. But for those of us who can use a bit of Clojure in their shell scripts, it may be useful.

Babashka runs as a binary and uses sci for interpreting Clojure, which results in faster startup times:

$ time clojure -e "(require '[ :as shell])" ./download_html.clj
2.15s user 0.17s system 242% cpu 0.959 total

$ time bb -f ./download_html.clj
0.00s user 0.00s system 69% cpu 0.010 total

A trade-off is that sci implements only a subset of Clojure. If you need more, feel free to post an issue or check out other Clojure scripting projects.


Experimental. Breaking changes are expected to happen at this phase.



Linux and macOS binaries are provided via brew.


brew install borkdude/brew/babashka


brew upgrade babashka

Installer script

Install via the installer script:

$ bash <(curl -s

By default this will install into /usr/local/bin. To change this, provide the directory name:

$ bash <(curl -s /tmp


You may also download a binary from Github.


bb [ --help ] | [ --version ] | ( [ -i ] [ -o ] | [ -io ] ) ( expression | -f <file> )

Type bb --help to see a full explanation of the options.

The input is read as EDN by default. If the -i flag is provided, then the input is read as a string which is then split on newlines. The output is printed as EDN by default, unless the -o flag is provided, then the output is turned into shell-scripting friendly output. To combine -i and -o you can use -io.

The clojure.core functions are accessible without a namespace alias.

The following Clojure namespaces are required by default and only available through the aliases:

  • clojure.string aliased as str
  • clojure.set aliased as set
  • clojure.edn aliased as edn (only read-string is available)
  • aliases as shell (only sh is available)

From Java the following is available:

  • System: exit, getProperty, getProperties, getenv

Special vars:

  • *in*: contains the input read from stdin
  • *command-line-args*: contain the command line args


$ ls | bb -i '*in*'
["LICENSE" "" "bb" "doc" "pom.xml" "project.clj" "reflection.json" "resources" "script" "src" "target" "test"]

$ ls | bb -i '(count *in*)'

$ bb '(vec (dedupe *in*))' <<< '[1 1 1 1 2]'
[1 2]

$ bb '(filterv :foo *in*)' <<< '[{:foo 1} {:bar 2}]'
[{:foo 1}]
$ bb '(#(+ %1 %2 %3) 1 2 *in*)' <<< 3
$ ls | bb -i '(filterv #(re-find #"reflection" %) *in*)'
$ bb '(run! #(shell/sh "touch" (str "/tmp/test/" %)) (range 100))'
$ ls /tmp/test | bb -i '*in*'
["0" "1" "10" "11" "12" "13" "14" "15" "16" "17" "18" "19" "2" "20" "21" ...]

More examples can be found in the gallery.

Running a file

Scripts may be executed from a file using -f or --file:

bb -f download_html.clj

Using bb with a shebang also works:

#!/usr/bin/env bb -f

(defn get-url [url]
  (println "Fetching url:" url)
  (let [{:keys [:exit :err :out]} (shell/sh "curl" "-sS" url)]
    (if (zero? exit) out
      (do (println "ERROR:" err)
          (System/exit 1)))))

(defn write-html [file html]
  (println "Writing file:" file)
  (spit file html))

(let [[url file] *command-line-args*]
  (when (or (empty? url) (empty? file))
    (println "Usage: <url> <file>")
    (System/exit 1))
  (write-html file (get-url url)))

(System/exit 0)
$ ./download_html.clj
Usage: <url> <file>

$ ./download_html.clj /tmp/
Fetching url:
Writing file: /tmp/


Test on the JVM:


Although this tool doesn't offer any benefit when running on the JVM, it is convenient for development.

Test the native version:

BABASHKA_TEST_ENV=native script/test


You will need leiningen and GraalVM.


Related projects


Here's a gallery of more useful examples. Do you have a useful example? PR welcome!

Shuffle the lines of a file

$ cat /tmp/test.txt
1 Hello
2 Clojure
3 Babashka
4 Goodbye

$ < /tmp/test.txt bb -io '(shuffle *in*)'
3 Babashka
2 Clojure
4 Goodbye
1 Hello

Fetch latest Github release tag

For converting JSON to EDN, see jet.

$ curl -s |
jet --from json --keywordize --to edn |
bb '(-> *in* first :name (subs 1))'

Get latest OS-specific download url from Github

$ curl -s |
jet --from json --keywordize |
bb '(-> *in* first :assets)' |
bb '(some #(re-find #".*linux.*" (:browser_download_url %)) *in*)'

Support this project

Do you enjoy this project? Consider buying me a hot beverage.


Copyright © 2019 Michiel Borkent

Distributed under the EPL License, same as Clojure. See LICENSE.