Run code in the Scala 2 language
[ <option> ]... [ <torun> <argument>... ]
scala command returns a zero exit status if it succeeds. Non zero is returned in case of any error. If a script or top-level object is executed and returns a value, then that return value is passed on to
Report bugs to
- Any scalac option. See scalac(1).
- How to execute <torun>, if it is present. Options for <how> are
- Requests that a file be pre-loaded. It is only meaningful for interactive shells.
- Requests that its argument be executed as Scala code.
- Save this compiled version of scripts in order to speed up later executions of the same script. When running a script, save the compiled version of in a file with the same name as the script but with an extension of
.jar. On subsequent runs of the same script, the pre-compiled
.jarfile will be used if it is newer than the script file.
- Do not use the fsc offline compiler.
- Set a Java system property. If no value is specified, then the property is set to the empty string.
- A top-level object or a script file to run.
- An arguments to pass to <torun>.
scala utility runs Scala code using a Java runtime environment. The Scala code to run is specified in one of three ways:
- With no arguments specified, a Scala shell starts and reads commands interactively.
-howtorun:objectspecified, the fully qualified name of a top-level Scala object may be specified. The object should previously have been compiled using scalac(1).
-howtorun:scriptspecified, a file containing Scala code may be specified.
-howtorun: is left as the default (
guess), then the
scala command will check whether a file of the specified name exists. If it does, then it will treat it as a script file; if it does not, then it will treat it as the name of an object.
In all three cases, arbitrary scalac options may be specified. The most common option is to specify a classpath with
-classpath, but see the scalac(1) page for full details.
If an object is specified to run, then that object must be a top-level Scala object with the specified name. The object must define a method main with the following signature:
def main(args: Array[String]): Unit
The method must return a Unit value, and it must accept a String array as a parameter. All arguments specified on the command line will be passed as arguments to the main method.
If a script file is specified to run, then the file is read and all Scala statements and declarations in the file are processed in order. Any arguments specified will be available via the
Script files may have an optional header that is ignored if present. There are two ways to format the header: either beginning with
#! and ending with
!#, or beginning with
::#! and ending with
Such a header must have each header boundary start at the beginning of a line. Headers can be used to make stand-alone script files, as shown in the examples below.
scala is run from an sbaz(1) directory, then it will add to its classpath any jars installed in the lib directory of the sbaz directory. Additionally, if no -classpath option is specified, then
scala will add ".", the current directory, to the end of the classpath.
If any compiler options are specified, they must be first in the command line and must be followed by a bare hypen ("-") character. If no arguments are specified after the optional compiler arguments, then an interactive Scala shell is started. Otherwise, either a script file is run, or a pre-compiled Scala object is run. It is possible to distinguish the last two cases by using an explicit
-script flag, but usually the program can guess correctly.
- Specify the
javacommand to be used for running the Scala code. Arguments may be specified as part of the environment variable; spaces, quotation marks, etc., will be passed directly to the shell for expansion.
- Specify JDK/JRE home directory. This directory is used to locate the
- Specify the options to be passed to the
javacommand defined by
JAVACMD. With Java 1.5 (or newer) one may for example configure the memory usage of the JVM as follows:
JAVA_OPTS="-Xmx512M -Xms16M -Xss16M"With GNU Java one may configure the memory usage of the GIJ as follows:
Here are some examples of running Scala code:
- Execute a Scala program generated in the current directory
- Execute a Scala program generated in a user-defined directory classes
- Execute a Scala program using a user-defined
- Execute a Scala program using JVM options
Here is a complete Scala script for Unix:
#!/bin/sh exec scala "$0" "$@" !# Console.println("Hello, world!") argv.toList foreach Console.println
Here is a complete Scala script for MS Windows:
::#! @echo off call scala %0 %* goto :eof ::!# Console.println("Hello, world!") argv.toList foreach Console.println
If you want to use the compilation cache to speed up multiple executions of the script, then add
-savecompiled to the scala command:
#!/bin/sh exec scala -savecompiled "$0" "$@" !# Console.println("Hello, world!") argv.toList foreach Console.println
This is open-source software, available to you under a BSD-like license. See accomponying "copyright" or "LICENSE" file for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
fsc(1), sbaz(1), scalac(1), scaladoc(1), scalap(1)
Written by Martin Odersky and other members of the Scala team.