Liking cljdoc? Tell your friends :D

CircleCI Clojars Project project chat

A Clojure babushka for the grey areas of Bash.


$ bash <(curl -s
$ ls | bb --time -i '(filter #(-> % io/file .isDirectory) *input*)'
("doc" "resources" "sci" "script" "src" "target" "test")
bb took 4ms.


The sweet spot for babashka is executing Clojure snippets or scripts in the same space where you would use Bash.

As one user described it:

I’m quite at home in Bash most of the time, but there’s a substantial grey area of things that are too complicated to be simple in bash, but too simple to be worth writing a clj/s script for. Babashka really seems to hit the sweet spot for those cases.


  • Fast startup / low latency. This is achieved by compiling to native using GraalVM.
  • Familiarity and portability. Keep migration barriers between bash and Clojure as low as possible by:
    • Gradually introducing Clojure expressions to existing bash scripts
    • Scripts written in babashka should also be able to run on the JVM without major changes.
  • Multi-threading support similar to Clojure on the JVM
  • Batteries included (, core.async, ...)


  • Performance
  • Provide a mixed Clojure/bash DSL (see portability).
  • Replace existing shells. Babashka is a tool you can use inside existing shells like bash and it is designed to play well with them. It does not aim to replace them.

Reasons why babashka may not be the right fit for your use case:

  • It uses sci for interpreting Clojure. Sci implements only a subset of Clojure and is not as performant as compiled code.
  • External libraries are not available (although you may use load-file for loading external scripts).

Read more about the differences with Clojure here.


Experimental. Breaking changes are expected to happen at this phase. Keep an eye on for a list of breaking changes.


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

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

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

$ bb '(filterv :foo *input*)' <<< '[{:foo 1} {:bar 2}]'
[{:foo 1}]

$ bb '(#(+ %1 %2 %3) 1 2 *input*)' <<< 3

$ ls | bb -i '(filterv #(re-find #"reflection" %) *input*)'

$ bb '(run! #(shell/sh "touch" (str "/tmp/test/" %)) (range 100))'
$ ls /tmp/test | bb -i '*input*'
["0" "1" "10" "11" "12" "13" "14" "15" "16" "17" "18" "19" "2" "20" "21" ...]

$ bb -O '(repeat "dude")' | bb --stream '(str *input* "rino")' | bb -I '(take 3 *input*)'
("duderino" "duderino" "duderino")

More examples can be found in the gallery.



Linux and macOS binaries are provided via brew.


brew install borkdude/brew/babashka


brew upgrade babashka

Arch (Linux)

babashka is available in the Arch User Repository. It can be installed using your favorite AUR helper such as yay, yaourt, apacman and pacaur. Here is an example using yay:

yay -S babashka-bin

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.


Usage: bb [ -i | -I ] [ -o | -O ] [ --stream ] [--verbose]
          [ ( --classpath | -cp ) <cp> ] [ ( --main | -m ) <main-namespace> ]
          ( -e <expression> | -f <file> | --repl | --socket-repl [<host>:]<port> )
          [ arg* ]


  --help, -h or -?   Print this help text.
  --version          Print the current version of babashka.
  -i                 Bind *input* to a lazy seq of lines from stdin.
  -I                 Bind *input* to a lazy seq of EDN values from stdin.
  -o                 Write lines to stdout.
  -O                 Write EDN values to stdout.
  --verbose          Print entire stacktrace in case of exception.
  --stream           Stream over lines or EDN values from stdin. Combined with -i or -I *input* becomes a single value per iteration.
  -e, --eval <expr>  Evaluate an expression.
  -f, --file <path>  Evaluate a file.
  -cp, --classpath   Classpath to use.
  -m, --main <ns>    Call the -main function from namespace with args.
  --repl             Start REPL
  --socket-repl      Start socket REPL. Specify port (e.g. 1666) or host and port separated by colon (e.g.
  --time             Print execution time before exiting.

If neither -e, -f, or --socket-repl are specified, then the first argument that is not parsed as a option is treated as a file if it exists, or as an expression otherwise.
Everything after that is bound to *command-line-args*.

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

The following namespaces are required by default and available through the pre-defined aliases in the user namespace. You may use require + :as and/or :refer on these namespaces. If not all vars are available, they are enumerated explicitly.

  • clojure.string aliased as str
  • clojure.set aliased as set
  • clojure.edn aliased as edn:
    • read-string
  • aliases as shell:
    • sh
  • aliased as io:
    • as-relative-path, as-url, copy, delete-file, file, input-stream, make-parents, output-stream, reader, writer
  • clojure.main: repl
  • clojure.core.async aliased as async. The alt and go macros are not available but alts!! does work as it is a function.
  • aliased as tools.cli
  • aliased as csv
  • cheshire.core aliased as json

The following Java classes are available:

  • ArithmeticException
  • AssertionError
  • Boolean
  • Class
  • Double
  • Exception
  • clojure.lang.ExceptionInfo
  • Integer
  • Math
  • java.nio.file.Files
  • java.util.Base64
  • java.util.regex.Pattern
  • ProcessBuilder (see example).
  • String
  • System
  • Thread

More classes can be added by request. See reflection.json and the :classes option in main.clj.

Babashka supports import : (import clojure.lang.ExceptionInfo).

Babashka supports a subset of the ns form where you may use :require and :import:

(ns foo
  (:require [clojure.string :as str])
  (:import clojure.lang.ExceptionInfo))

For the unsupported parts of the ns form, you may use reader conditionals to maintain compatibility with JVM Clojure.

Input and output flags

In one-liners the *input* value may come in handy. It contains the input read from stdin as EDN by default. If you want to read in text, use the -i flag, which binds *input* to a lazy seq of lines of text. If you want to read multiple EDN values, use the -I flag. The -o option prints the result as lines of text. The -O option prints the result as lines of EDN values.

The following table illustrates the combination of options for commands of the form

echo "{{Input}}" | bb {{Input flags}} {{Output flags}} "*input*"
Input Input flags Output flag *input* Output
{:a 1}
{:a 2}
{:a 1} {:a 1}
-i ("hello" "bye") ("hello" "bye")
-i -o ("hello" "bye") hello
{:a 1}
{:a 2}
-I ({:a 1} {:a 2}) ({:a 1} {:a 2})
{:a 1}
{:a 2}
-I -O ({:a 1} {:a 2}) {:a 1}
{:a 2}

When combined with the --stream option, the expression is executed for each value in the input:

$ echo '{:a 1} {:a 2}' | bb --stream '*input*'
{:a 1}
{:a 2}

Current file path

The var *file* contains the full path of the file that is currently being executed:

$ cat example.clj
(prn *file*)

$ bb example.clj

Command-line arguments

Command-line arguments can be retrieved using *command-line-args*.

Additional functions

Additionally, babashka adds the following functions:

  • wait/wait-for-port. Usage:
(wait/wait-for-port "localhost" 8080)
(wait/wait-for-port "localhost" 8080 {:timeout 1000 :pause 1000})

Waits for TCP connection to be available on host and port. Options map supports :timeout and :pause. If :timeout is provided and reached, :default's value (if any) is returned. The :pause option determines the time waited between retries.

  • wait/wait-for-path. Usage:
(wait/wait-for-path "/tmp/wait-path-test")
(wait/wait-for-path "/tmp/wait-path-test" {:timeout 1000 :pause 1000})

Waits for file path to be available. Options map supports :default, :timeout and :pause. If :timeout is provided and reached, :default's value (if any) is returned. The :pause option determines the time waited between retries.

  • sig/pipe-signal-received?. Usage:

Returns true if PIPE signal was received. Example:

$ bb '((fn [x] (println x) (when (not (sig/pipe-signal-received?)) (recur (inc x)))) 0)' | head -n2

Running a file

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

bb -f download_html.clj

Files can also be loaded inline using load-file:

bb '(load-file "script.clj")'

Using bb with a shebang also works:

#!/usr/bin/env bb

(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/

If /usr/bin/env doesn't work for you, you can use the following workaround:

$ cat script.clj

   "exec" "bb" "$0" hello "$@"

(prn *command-line-args*)

./script.clj 1 2 3
("hello" "1" "2" "3")


The environment variable BABASHKA_PRELOADS allows to define code that will be available in all subsequent usages of babashka.

BABASHKA_PRELOADS='(defn foo [x] (+ x 2))'

Note that you can concatenate multiple expressions. Now you can use these functions in babashka:

$ bb '(-> (foo *input*) bar)' <<< 1

You can also preload an entire file using load-file:

export BABASHKA_PRELOADS='(load-file "my_awesome_prelude.clj")'

Note that *input* is not available in preloads.


Babashka accepts a --classpath option that will be used to search for namespaces and load them:

$ cat src/my/namespace.clj
(ns my.namespace)
(defn -main [& _args]
  (println "Hello from my namespace!"))

$ bb --classpath src --main my.namespace
Hello from my namespace!

Note that you can use the clojure tool to produce classpaths and download dependencies:

$ cat deps.edn
    {:git/url ""
     :sha "cfc761d06dfb30bb77166b45d439fe8fe54a31b8"}}}

$ CLASSPATH=$(clojure -Spath)
$ bb --classpath "$CLASSPATH" --main my-gist-script
Hello from gist script!

If there is no --classpath argument, the BABASHKA_CLASSPATH environment variable will be used:

$ export BABASHKA_CLASSPATH=$(clojure -Spath)
$ export BABASHKA_PRELOADS="(require '[my-gist-script])"
$ bb "(my-gist-script/-main)"
Hello from gist script!

Parsing command line arguments

Babashka ships with

(require '[ :refer [parse-opts]])

(def cli-options
  ;; An option with a required argument
  [["-p" "--port PORT" "Port number"
    :default 80
    :parse-fn #(Integer/parseInt %)
    :validate [#(< 0 % 0x10000) "Must be a number between 0 and 65536"]]
   ["-h" "--help"]])

(:options (parse-opts *command-line-args* cli-options))
$ bb script.clj
{:port 80}
$ bb script.clj -h
{:port 80, :help true}

Reader conditionals

Babashka supports reader conditionals using the :bb feature:

$ cat example.clj
#?(:clj (in-ns 'foo) :bb (println "babashka doesn't support in-ns yet!"))

$ ./bb example.clj
babashka doesn't support in-ns yet!

Socket REPL

Start the socket REPL like this:

$ bb --socket-repl 1666
Babashka socket REPL started at localhost:1666

Now you can connect with your favorite socket REPL client:

$ rlwrap nc 1666
Babashka v0.0.14 REPL.
Use :repl/quit or :repl/exit to quit the REPL.
Clojure rocks, Bash reaches.

bb=> (+ 1 2 3)
bb=> :repl/quit

A socket REPL client for Emacs is inf-clojure.

Spawning and killing a process

Use the java.lang.ProcessBuilder class.


user=> (def ws (-> (ProcessBuilder. ["python" "-m" "SimpleHTTPServer" "1777"]) (.start)))
user=> (wait/wait-for-port "localhost" 1777)
{:host "localhost", :port 1777, :took 2}
user=> (.destroy ws)

Also see this example.


Apart from future and pmap for creating threads, you may use the async namespace, which maps to clojure.core.async, for asynchronous scripting. The following example shows how to get first available value from two different processes:

bb '
(defn async-command [& args]
  (async/thread (apply shell/sh "bash" "-c" args)))

(-> (async/alts!! [(async-command "sleep 2 && echo process 1")
                   (async-command "sleep 1 && echo process 2")])
    first :out str/trim println)'
process 2

Differences with Clojure

Babashka is implemented using the Small Clojure Interpreter. This means that a snippet or script is not compiled to JVM bytecode, but executed form by form by a runtime which implements a subset of Clojure. Babashka is compiled to a native binary using GraalVM. It comes with a selection of built-in namespaces and functions from Clojure and other useful libraries. The data types (numbers, strings, persistent collections) are the same. Multi-threading is supported (pmap, future).

Differences with Clojure:

  • A subset of Java classes are supported.

  • Only the clojure.core, clojure.set, clojure.string and clojure.walk namespaces are available from Clojure.

  • Interpretation comes with overhead. Therefore tight loops are likely slower than in Clojure on the JVM.

  • No support for unboxed types.

External resources

Tools and libraries

The following libraries are known to work with Babashka:


A port of the clojure bash script to Clojure / babashka.


This fork does not depend on any other libraries. Example:

$ export BABASHKA_CLASSPATH="$(clojure -Sdeps '{:deps {limit-break {:git/url "" :sha "f44ebe45446f0f44f2b73761d102af3da6d0a13e"}}}' -Spath)"

$ bb "(require '[clj-http.lite.client :as client]) (:status (client/get \"\"))"


A debug REPL library. Example:

$ export BABASHKA_CLASSPATH="$(clojure -Sdeps '{:deps {limit-break {:git/url "" :sha "050fcfa0ea29fe3340927533a6fa6fffe23bfc2f" :deps/manifest :deps}}}' -Spath)"

$ bb "(require '[limit.break :as lb]) (let [x 1] (lb/break))"
Babashka v0.0.49 REPL.
Use :repl/quit or :repl/exit to quit the REPL.
Clojure rocks, Bash reaches.

break> x


Developing Babashka

To work on Babashka itself make sure Git submodules are checked out.

$ git clone --recursive

To update later on:

$ git submodule update --recursive

You need Leiningen, and for building binaries you need GraalVM.


lein repl will get you a standard REPL/nREPL connection. To work on tests use lein with-profiles +test repl.

Generate reflection.json file

lein with-profiles +reflection run


Test on the JVM (for development):


Test the native version:

BABASHKA_TEST_ENV=native script/test


To build this project, set $GRAALVM_HOME to the GraalVM distribution directory.

Then run:


Related projects


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

Delete a list of files returned by a Unix command

find . | grep conflict | bb -i '(doseq [f *input*] (.delete (io/file f)))'

Calculate aggregate size of directory

#!/usr/bin/env bb

(as-> (io/file (or (first *command-line-args*) ".")) $
  (file-seq $)
  (map #(.length %) $)
  (reduce + $)
  (/ $ (* 1024 1024))
  (println (str (int $) "M")))
$ dir-size

$ dir-size ~/Dropbox/bin

Shuffle the lines of a file

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

$ < /tmp/test.txt bb -io '(shuffle *input*)'
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 '(-> *input* first :name (subs 1))'

Get latest OS-specific download url from Github

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

View download statistics from Clojars

Contributed by @plexus.

$ curl |
bb -o '(for [[[group art] counts] *input*] (str (reduce + (vals counts))  " " group "/" art))' |
sort -rn |
14113842 clojure-complete/clojure-complete
9065525 clj-time/clj-time
8504122 cheshire/cheshire

Portable tree command

See examples/tree.clj.

$ clojure -Sdeps '{:deps {org.clojure/tools.cli {:mvn/version "0.4.2"}}}' examples/tree.clj src
└── babashka
    ├── impl
    │   ├── tools
    │   │   └── cli.clj

$ examples/tree.clj src
└── babashka
    ├── impl
    │   ├── tools
    │   │   └── cli.clj

List outdated maven dependencies

See examples/outdated.clj. Inspired by an idea from @seancorfield.

$ cat /tmp/deps.edn
{:deps {cheshire {:mvn/version "5.8.1"}
        clj-http {:mvn/version "3.4.0"}}}

$ examples/outdated.clj /tmp/deps.edn
clj-http/clj-http can be upgraded from 3.4.0 to 3.10.0
cheshire/cheshire can be upgraded from 5.8.1 to 5.9.0

Convert project.clj to deps.edn

Contributed by @plexus.

$ cat project.clj |
sed -e 's/#=//g' -e 's/~@//g' -e 's/~//g' |
bb '(let [{:keys [dependencies source-paths resource-paths]} (apply hash-map (drop 3 *input*))]
  {:paths (into source-paths resource-paths)
   :deps (into {} (for [[d v] dependencies] [d {:mvn/version v}]))}) ' |
jet --pretty > deps.edn

Print current time in California

See examples/pst.clj


  • adgoji for financial support


Copyright © 2019 Michiel Borkent

Distributed under the EPL License. See LICENSE.

This project contains code from:

  • Clojure, which is licensed under the same EPL License.

Can you improve this documentation? These fine people already did:
Michiel Borkent, Arne Brasseur, Nikita Prokopov, Nate Sutton, David Harrigan, sogaiu & Peter Strömberg
Edit on GitHub

cljdoc is a website building & hosting documentation for Clojure/Script libraries

× close