Coursier

2.0.0-RC6-3

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launch

Like the fetch command, launch resolves and fetches the artifacts of one or more dependencies. Unlike fetch, it doesn't stop there, and proceeds to actually launch the dependencies it fetched, like

$ coursier launch io.get-coursier:http-server_2.12:1.0.0

The launch command runs the dependencies it fetched in its own JVM. It simply loads them in a fresh class loader, loads the main class by reflection, and calls its main method.

Arguments

Pass arguments to the launched program, by adding -- after the coursier arguments, like

$ coursier launch com.geirsson:scalafmt-cli_2.12:1.5.1 -- --version

Main class

The main class to launch from the passed dependencies must be either specified on the command-line, via the -M option, like

$ coursier launch com.lihaoyi:ammonite_2.12.8:1.6.0 -M ammonite.Main

or must be specified in the manifest of one of the loaded JARs.

If the project of the main class relies on sbt, and contains only one main class, its manifest should already contain this main class name (it's added out-of-the-box). In case of several main classes, one should set the mainClass setting to the right value, for the main class to be specified in the manifest.

In case several of the loaded JARs have manifests with main classes, the launch command applies an heuristic to try to find the "main" one.

If ever that heuristic fails, run the launch command with the -v option specified twice, like

$ coursier launch com.geirsson:scalafmt-cli_2.12:1.5.1 -r bintray:scalameta/maven -v -v -- --version
…
Found main classes:
  com.martiansoftware.nailgun.NGServer (vendor: , title: )
  org.scalafmt.cli.Cli (vendor: com.geirsson, title: cli)
…

It should print the main classes it found. Then, replace -v -v with -M main.class.of.your.choice, like

$ coursier launch com.geirsson:scalafmt-cli_2.12:1.5.1 -r bintray:scalameta/maven -M org.scalafmt.cli.Cli -- --version

Java options

On Linux / OS X, recent versions of the coursier launcher accept Java options, prefixed with -J, like

$ coursier -J-Dfoo=bar -J-Xmx2g launch com.lihaoyi:ammonite_2.12.8:1.6.0 -M ammonite.Main
Loading...
Welcome to the Ammonite Repl 1.6.0
(Scala 2.12.8 Java 1.8.0_121)
@ sys.props("foo")
res0: String = "bar"

Alternatively, run java explicitly, and pass it the options you'd like, e.g.

$ java -Dfoo=bar -Xmx2g -jar "$(which coursier)" launch com.lihaoyi:ammonite_2.12.8:1.6.0 -M ammonite.Main
Loading...
Welcome to the Ammonite Repl 1.6.0
(Scala 2.12.8 Java 1.8.0_121)
@ sys.props("foo")
res0: String = "bar"

From the Windows command, only the second way should work, like

> java -Dfoo=bar -jar /path/to/coursier launch com.lihaoyi:ammonite_2.12.8:1.6.0 -M ammonite.Main

Examples

Ammonite

$ ./coursier launch com.lihaoyi:ammonite_2.12.8:1.6.0 -M ammonite.Main

Frege

$ ./coursier launch -r central -r https://oss.sonatype.org/content/groups/public \
    org.frege-lang:frege-repl-core:1.3 -M frege.repl.FregeRepl

clojure

$ ./coursier launch org.clojure:clojure:1.7.0 -M clojure.main

jruby

$ wget https://raw.githubusercontent.com/jruby/jruby/master/bin/jirb && \
  ./coursier launch org.jruby:jruby:9.0.4.0 -M org.jruby.Main -- -- jirb

jython

$ ./coursier launch org.python:jython-standalone:2.7.0 -M org.python.util.jython

Groovy

$ ./coursier launch org.codehaus.groovy:groovy-groovysh:2.4.5 -M org.codehaus.groovy.tools.shell.Main \
    commons-cli:commons-cli:1.3.1

ProGuard

$ ./coursier launch net.sf.proguard:proguard-base:5.2.1 -M proguard.ProGuard
$ ./coursier launch net.sf.proguard:proguard-retrace:5.2.1 -M proguard.retrace.ReTrace

Wiremock

./coursier launch com.github.tomakehurst:wiremock:1.57 -- \
--proxy-all="http://search.twitter.com" --record-mappings --verbose

SQLLine

$ ./coursier launch \
  sqlline:sqlline:1.3.0 \
  org.postgresql:postgresql:42.1.4 \
  -M sqlline.SqlLine -- \
  -d org.postgresql.Driver \
  -n USERNAME \
  -p PASSWORD \
  -u jdbc:postgresql://HOST:PORT/DATABASE
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