kscriptScripting enhancements for Kotlin
kscript - Having fun with Kotlin scripting
Enhanced scripting support for Kotlin on *nix-based systems.
Kotlin has some built-in support for scripting already but it is not yet feature-rich enough to be a viable alternative in the shell.
In particular this wrapper around kotlinc
adds
- Compiled script caching (using md5 checksums)
- Dependency declarations using gradle-style resource locators and automatic dependency resolution with jcabi-aether
- More options to provide scripts including interpreter mode, reading from stdin, local files or URLs
- Embedded configuration for Kotlin runtime options
- Support library to ease the writing of Kotlin scriptlets
- Deploy scripts as stand-alone binaries
Taken all these features together, kscript
provides an easy-to-use, very flexible, and almost zero-overhead solution to write self-contained mini-applications with Kotlin.
Good News: Kotlin v1.4 finally ships with a much improved - and needed - scripting integration. See here for examples and documentation. Still, we think that kscript
has various benefits compared this new platform-bundled improved toolstack, so we'll plan to support kscript
until the kotlin platform will ship with an even more rich and versatile kotlin scripting interpreter.
kscript
presentation from KotlinConf2017!
- Installation
- Script Input Modes
- Script Configuration
- Text Processing Mode
- Treat yourself a REPL with
--interactive
- Boostrap IDEA from a
kscript
let - Deploy scripts as standalone binaries
- Embed kscript installer within your script
- FAQ
- Support
- How to contribute?
- Acknowledgements
Installation
To use kscript
just Kotlin and Maven are required. To install Kotlin we recommend sdkman:
curl -s "https://get.sdkman.io" | bash # install sdkman
source "$HOME/.sdkman/bin/sdkman-init.sh" # add sdkman to PATH
sdk install kotlin # install Kotlin
Once Kotlin is ready, you can install kscript
with
sdk install kscript
To test your installation simply run
kscript --help
This will check and inform about updates. To update kscript
simply install it again as described above.
Run with docker
We provide an executable docker container to run kscript
# using the latest version of kscript
docker run -i holgerbrandl/kscript 'println("Hello, world!")'
# or using versioned container
docker run -i holgerbrandl/kscript:2.9.3 'println("Hello, world!")'
To use a script file outside of the container as input, you could do
docker run -i holgerbrandl/kscript - < script.kts
This will make kscript
read the code from stdin while piping the file. Beware that the -i flag is needed to have stdout redirected outside the container.
Please note, that currently @Include
are not supported when using a dockerized kscript. Also, any resource outside the container context may not be resolved correctly. To overcome this limitation, you could use for instance bind mounts.
sdkman
Installation without If you have Kotlin and Maven already and you would like to install the latest kscript
release without using sdkman
you can do so by unzipping the latest binary release. Don't forget to update your $PATH
accordingly.
Installation with Homebrew
On MacOS you can install kscript
also with Homebrew
brew install holgerbrandl/tap/kscript
To upgrade to latest version
brew update
brew upgrade holgerbrandl/tap/kscript
Installation on Arch Linux
On Arch Linux, kscript
is available through the Arch Linux User repository (AUR). Use your favorite AUR helper to install, e.g. yay
:
yay -S kscript
Build it yourself
To build kscript
yourself, simply clone the repo and do
./gradlew assemble
## Run kscript from output dir
./build/libs/kscript
Script Input Modes
The main mode of operation is kscript <script>
.
The <script>
can be a Kotlin *.kts
script file , a script URL, -
for stdin, a process substitution file handle, a *.kt
source file with a main method, or some kotlin code.
Interpreter Usage
To use kscript
as interpreter for a script just point to it in the shebang line of your Kotlin scripts:
#!/usr/bin/env kscript
println("Hello from Kotlin!")
for (arg in args) {
println("arg: $arg")
}
Inlined Usage
To use kscript
in a workflow without creating an additional script file, you can also use one of its supported modes for inlined usage. The following modes are supported:
- Directly provide a Kotlin scriptlet as argument
kscript 'println("hello world")'
- Pipe a Kotlin snippet into
kscript
and instruct it to read fromstdin
by using-
as script argument
echo '
println("Hello Kotlin.")
' | kscript -
- Using
heredoc
(preferred solution for inlining) which gives you some more flexibility to also use single quotes in your script:
kscript - <<"EOF"
println("It's a beautiful day!")
EOF
- Since the piped content is considered as a regular script it can also have dependencies
kscript - <<"EOF"
//DEPS com.offbytwo:docopt:0.6.0.20150202 log4j:log4j:1.2.14
import org.docopt.Docopt
val docopt = Docopt("Usage: jl <command> [options] [<joblist_file>]")
println("hello again")
EOF
- Finally (for sake of completeness), it also works with process substitution and for sure you can always provide additional arguments (exposed as
args : Array<String>
within the script)
kscript <(echo 'println("k-onliner")') arg1 arg2 arg3
Inlined kscripts are also cached based on md5
checksum, so running the same snippet again will use a cached jar (sitting in ~/.kscript
).
URL usage
To support remote scriplet repositories, kscript
can also work with URLs. Consider the following hello-world-gist-scriptlet which is hosted on github (but any URL would work). To run it locally as a tool simply refer to it (here using the shortened raw-URL of the script for better readability)
kscript https://git.io/v1cG6 my argu ments
To streamline the usage, the first part could be even aliased:
alias hello_kscript="kscript https://git.io/v1cG6"
hello_kscript my argu ments
Via this mechanism, kscript
allows for easy integration of remotely hosted (mini) programs into data workflows.
URL-scripts are cached locally to speed up processing, and kscript --clear-cache
can be used to wipe the cache if needed.
See this blogpost for a more extensive overview about URL support in kscript
.
Script Configuration
The following directives supported by kscript
to configure scripts:
-
//DEPS
to declare dependencies with gradle-style locators -
//KOTLIN_OPTS
to configure the kotlin/java runtime environment -
//INCLUDE
to source kotlin files into the script -
//ENTRY
to declare the application entrypoint for kotlin*.kt
applications
//DEPS
Declare dependencies with To specify dependencies simply use gradle-style locators. Here's an example using docopt and log4j
#!/usr/bin/env kscript
//DEPS com.offbytwo:docopt:0.6.0.20150202,log4j:log4j:1.2.14
import org.docopt.Docopt
import java.util.*
val usage = """
Use this cool tool to do cool stuff
Usage: cooltool.kts [options] <igenome> <fastq_files>...
Options:
--gtf <gtfFile> Custom gtf file instead of igenome bundled copy
--pc-only Use protein coding genes only for mapping and quantification
"""
val doArgs = Docopt(usage).parse(args.toList())
println("Hello from Kotlin!")
println("Parsed script arguments are: \n" + doArgs)
kscript
will read dependencies from all lines in a script that start with //DEPS
(if any). Multiple dependencies can be split by comma, space or semicolon.
//KOTLIN_OPTS
Configure the runtime with kscript
allows to provide a //KOTLIN_OPTS
directive followed by parameters passed on to kotlin
similar to how dependencies are defined:
#!/usr/bin/env kscript
//KOTLIN_OPTS -J-Xmx5g -J-server
println("Hello from Kotlin with 5g of heap memory running in server mode!")
Note: Similar to the runtime you can also tweak the compile step by providing //COMPILER_OPTS
.
//INCLUDE
Ease prototyping with kscript
supports an //INCLUDE
directive to directly include other source files without prior compilation. Absolute and relative paths, as well as URLs are supported. Example:
//utils.kt
fun Array<Double>.median(): Double {
val (lower, upper) = sorted().let { take(size / 2) to takeLast(size / 2) }
return if (size % 2 == 0) (lower.last() + upper.first()) / 2.0 else upper.first()
}
Which can be now used using the //INCLUDE
directive with
#!/usr/bin/env kscript
//INCLUDE utils.kt
val robustMean = listOf(1.3, 42.3, 7.).median()
println(robustMean)
The argument can be an URL, absolute or relative file path. Note that URLs used in include directives are cached locally to speed up processing, that is kscript
won't fetch URLs again unless the user actively clears the cache with kscript --clear-cache
.
For more examples see here.
//ENTRY
to run applications with main
method
Use kscript
also supports running regular Kotlin kt
files.
Example: ./examples/Foo.kt
:
package examples
//ENTRY examples.Bar
class Bar{
companion object {
@JvmStatic fun main(args: Array<String>) {
println("Foo was called")
}
}
}
fun main(args: Array<String>) = println("main was called")
To run top-level main instead we would use //ENTRY examples.FooKt
The latter is the default for kt
files and could be omitted
Annotation driven script configuration
Using annotations instead of comment directives to configure scripts is cleaner and allow for better tooling.
// annotation-driven script configuration
@file:DependsOn("com.github.holgerbrandl:kutils:0.12")
// comment directive
//DEPS com.github.holgerbrandl:kutils:0.12
To do so kscript
supports annotations to be used instead of comment directives:
#!/usr/bin/env kscript
// Declare dependencies
@file:DependsOn("com.github.holgerbrandl:kutils:0.12")
@file:DependsOn("com.beust:klaxon:0.24", "com.github.kittinunf.fuel:fuel:2.3.1")
// To use a custom maven repository you can declare it with
@file:MavenRepository("imagej-releases","http://maven.imagej.net/content/repositories/releases" )
// For compatibility with https://github.com/ligee/kotlin-jupyter kscript supports also
@file:DependsOnMaven("net.clearvolume:cleargl:2.0.1")
// Note that for compatibility reasons, only one locator argument is allowed for @DependsOnMaven
// also protected artifact repositories are supported, see <https://github.com/holgerbrandl/kscript/blob/master/test/TestsReadme.md#manual-testing>
// @file:MavenRepository("my-art", "http://localhost:8081/artifactory/authenticated_repo", user="auth_user", password="password")
// You can use environment variables for user and password when string surrounded by double {} brackets
// @file:MavenRepository("my-art", "http://localhost:8081/artifactory/authenticated_repo", user="{{ARTIFACTORY_USER}}", password="{{ARTIFACTORY_PASSWORD}}")
// will be use 'ARTIFACTORY_USER' and 'ARTIFACTORY_PASSWORD' environment variables
// if the value doesn't found in the script environment will fail
// Include helper scripts without deployment or prior compilation
@file:Include("util.kt")
// Define kotlin options
@file:KotlinOpts("-J-Xmx5g")
@file:KotlinOpts("-J-server")
@file:CompilerOpts("-jvm-target 1.8")
// declare application entry point (applies on for kt-files)
@file:EntryPoint("Foo.bar")
print("1+1")
To enable the use of these annotations in Intellij, the user must add the following artifact to the project dependencies:
com.github.holgerbrandl:kscript-annotations:1.2
kscript
will automatically detect an annotation-driven script, and if so will declare a dependency on this artifact internally.
Note, that if a script is located in a package other than the root package, you need to import the annotations with (e.g. import DependsOn
).
Text Processing Mode
kscript
can be used as a speedier and more flexible substitute for built-in terminal text tools such as awk
or sed
. Its text processing mode can be enabled with -t
or --text
. If so, kscript
will
- Declare
com.github.holgerbrandl:kscript-support-api:1.2.5
as dependency for the script. This support library eases the writing of Kotlin scriptlets for text-processing. It includes solutions to common use-cases like argument parsing, data streaming, IO utilities, and various iterators to streamline the writing of scriptlets for text processing. - Import the
kscript.*
namespace - Define variable
val lines = kscript.text.resolveArgFile(args)
which returns an iterator over the lines in the first input argument of the script, or the standard input if no file arguments are provided to the script
This allows to to replace awk
ward constructs (or sed
orperl
) with kotlinesque solutions such as
cat some_file | kscript -t 'lines
.filter { "^de0[-0]*".toRegex().matches(it) }
.map { it + "foo:" }
.print()
'
In this example, the extension method Iterable<String>.print()
to print the lines to stdout comes from the support API. The rest is stdlib Kotlin.
For more examples using the support library see this blog post.
--interactive
Treat yourself a REPL with To create an interactive kotlin shell (aka REPL) with all script dependencies added to the classpath you can use --interactive
.
For example, let's assume the following short script, named CountRecords.kts
#!/usr/bin/env kscript
@file:DependsOn("com.github.holgerbrandl:kutils:0.12")
import de.mpicbg.scicomp.bioinfo.openFasta
if (args.size != 1) {
System.err.println("Usage: CountRecords <fasta>")
kotlin.system.exitProcess(-1)
}
val records = openFasta(java.io.File(args[0]))
println(records.count())
To build a REPL that has the declared artifact in its classpath, we can just do
kscript --interactive CountRecords.kts
which will bring up the classpath-enhanced REPL:
Creating REPL from CountRecords.kts
Welcome to Kotlin version 1.1.51 (JRE 1.8.0_151-b12)
>>> import de.mpicbg.scicomp.bioinfo.openFasta
>>>
kscript
let
Boostrap IDEA from a Artifacts and versions will differ between scripts, so it is hard to maintain them all in a single project. To nevertheless provide optimal tooling when scripting with Kotlin kscript
allows to create temporary projects for <script>
arguments. .
kscript --idea CountRecords.kts
This will open IntelliJ IDEA with a minimalistic project containing just your (1) <script>
and (2) a generated gradle.build
file:
This assumes that you have the Intellij IDEA command line launcher idea
in your PATH
. It can be created in IntelliJ under Tools -> Create Command-line Launcher
or you can set the command used to launch your intellij as KSCRIPT_IDEA_COMMAND
env property
Deploy scripts as standalone binaries
To deploy a script simply do
kscript --package some_script.kts
./some_script --arg u ments
The created binary will contain a compiled copy of the script, as well as all declared dependencies (fatjar). Also runtime jvm parameters declared via @file:KotlinOpts
are used to spin up the JVM.
Just java
is required to run these binaries.
Embed kscript installer within your script
To make a script automatically install kscript and its dependencies on first run if necessary, run:
kscript --add-bootstrap-header some_script.kts
Now some_script.kts
can be shared and run directly on any other machine that has bash
, without having to go through the Installation steps first.
Note that unlike the --package
option this doesn't produce a separate file, allowing the distributed script to be read and modified(including with kscript --idea
) similar to what you might expect with bash/python/ruby scripts. On the other hand this doesn't embed dependencies within the script("fat jar"), so internet connection may be required on its first run.
FAQ
kscript
not calling the main method in my .kts
script?
Why is There is no need for a main
method in a Kotlin script. Kotlin *.kts
scripts can be more simplistic compared to more common kotlin *.kt
source files. The former work without a main
method by directly running the provided code from top to bottom. E.g.
print("hello kotlin!")
is a valid Kotlin kts
script. Plain and simple, no main
, no companion
, just a few bits of code.
kscript
also work for regular kotlin .kt
source files with a main
as entry point?
Does Yes, (since v1.6) you can run kotlin source files through kscript
. By default it will assume a top-level main
method as entry-point.
However in case you're using a companion object to declare the entry point, you need to indicate this via the //ENTRY
/@file:Entry
directive:
Why does it fail to read my script file when using cygwin?
In order to use cygwin you need to use windows paths to provide your scripts. You can map cygwin paths using cygpath
. Example
kscript $(cygpath -w /cygdrive/z/some/path/my_script.kts)
What are performance and resource usage difference between scripting with kotlin and python?
Kotlin is a compiled language, so there is a compilation overhead when you run a script/application written in Kotlin for the first time.
Kotlin runs (mainly) on the JVM which needs some time (~200ms) to start up. In contrast, the python interpreter has close to zero warmup time.
I think there is a consensus that JVM programs execute much faster than python equivalents. Still, python might be faster depending on your specific usecase. Also, with kotlin-native becoming more mature, you could compile into native binaries directly, which should bring it close to C/C++ performance.
Main motivations for using Kotlin over Python for scripting and development are
- Kotlin is the better designed, more fluent language with much better tooling around it
- The JVM dependency ecosystem allows for strict versioning. No more messing around with virtualenv, e.g. to run a short 10liner against a specific version of numpy.
Does kscript work with java?
The only language supported by kscript
is kotlin. For a similar approach centering around Java scripting see jbang.
Can I use custom artifact repositories?
Yes, via the @MavenRepository
annotation. See annotations section or custom_mvn_repo_annot for a complete example
Support
Feel welcome to post ideas and suggestions to our tracker.
More advanced use-cases are documented in the complementary user guide
How to contribute?
We always welcome pull requests and trouble tickets. :-)
Help to spread the word. Great community articles about kscript
include
- Type-safety in the shell with kscript
- Using Kotlin kscript for Preprocessing Data
- kscript as substitute for awk
- A complete backend with Kotlin and your favourite text-editor -using kscript
You could also show your support by upvoting kscript
here on github, or by voting for issues in Intellij IDEA which impact kscript
ing. Here are our top 2 tickets/annoyances that we would love to see fixed:
- KT-13347 Good code is red in injected kotlin language snippets
To allow for more interactive script development, you could also vote/comment on the most annoying REPL issues.
- KT-24789 "Unresolved reference" when running a script which is a symlink to a script outside of source roots
- KT-12583 IDE REPL should run in project root directory
- KT-11409 Allow to "Send Selection To Kotlin Console"
Acknowledgements
The initial version of kscript
was kindly contributed by Oscar Gonzalez.
Special thanks to Ilan Pillemer, Andrey Mischenko , Stephen Byrne, Eugene Susla, Eli Hart, Hwijae Lee and oshai for contributing PRs to this repo.
Thanks also to the Scionics Computer Innovation GmbH and the MPI-CBG for supporting this project.
kscript
was inspired by kotlin-script which is another great way (now deprecated) to do scripting in Kotlin.