scala(1) USER COMMANDS scala(1)NAMEscala - Run code in the Scala 2 language
SYNOPSISscala [ <option> ]... [ <torun> <argument>... ]
PARAMETERS
<compiler-option>
Any scalac option. See scalac(1).
-howtorun:<how>
How to execute <torun>, if it is present. Options for <how> are
guess (the default), script, jar, and object.
-i <file>
Requests that a file be pre-loaded. It is only meaningful for
interactive shells.
-e <string>
Requests that its argument be executed as Scala code.
-savecompiled
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 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 .jar file will be used if it is newer
than the script file.
-nocompdaemon
Do not use the fsc offline compiler.
-Dproperty=value
Set a Java system property. If no value is specified, then the
property is set to the empty string.
<torun>
A top-level object or a script file to run.
<argument>
An arguments to pass to <torun>.
DESCRIPTION
The scala utility runs Scala code using a Java runtime environment.
The Scala code to run is specified in one of three ways:
1. With no arguments specified, a Scala shell starts and reads com‐
mands interactively.
2. With -howtorun:object specified, the fully qualified name of a
top-level Scala object may be specified. The object should pre‐
viously have been compiled using scalac(1).
3. With -howtorun:script specified, a file containing Scala code
may be specified.
If -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 argsvariable.
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.
If 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 direc‐
tory. Additionally, if no -classpath option is specified, then scala
will add ".", the current directory, to the end of the classpath.
OPTIONS
If any compiler options are specified, they must be first in the com‐
mand 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 distin‐
guish the last two cases by using an explicit -object or -script flag,
but usually the program can guess correctly.
ENVIRONMENT
JAVACMD
Specify the java command 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.
JAVA_HOME
Specify JDK/JRE home directory. This directory is used to locate
the java command unless JAVACMD variable set.
JAVA_OPTS
Specify the options to be passed to the java command defined by
JAVACMD.
With Java 1.5 (or newer) one may for example configure the mem‐
ory 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: JAVA_OPTS="--mx512m --ms16m"
EXAMPLES
Here are some examples of running Scala code:
Execute a Scala program generated in the current directory
scala hello.HelloWorld
Execute a Scala program generated in a user-defined directory classes
scala-classpath classes hello.HelloWorld
Execute a Scala program using a user-defined java command
env JAVACMD=/usr/local/bin/cacao scala-classpath classes
hello.HelloWorld
Execute a Scala program using JVM options
env JAVACMD=java JAVA_OPTS="-Dmsg=hello -enableassertions" scala-classpath classes hello.HelloWorld
Here is a complete Scala script for Unix:
#!/bin/sh
exec scala "$0" "$@"
!#
Console.println("Hello, world!")
args.toList foreach Console.println
Here is a complete Scala script for MS Windows:
::#!
@echo off
call scala %0 %*
goto :eof
::!#
Console.println("Hello, world!")
args.toList foreach Console.println
If you want to use the compilation cache to speed up multiple execu‐
tions of the script, then add -savecompiled to the scala command:
#!/bin/sh
exec scala-savecompiled "$0" "$@"
!#
Console.println("Hello, world!")
args.toList foreach Console.println
EXIT STATUS
The 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
scala.
AUTHOR
Written by Martin Odersky and other members of the Scala team.
REPORTING BUGS
Report bugs to https://issues.scala-lang.org/.
COPYRIGHT
This is open-source software, available to you under a BSD-like
license. See accompanying "copyright" or "LICENSE" file for copying
conditions. There is NO warranty; not even for MERCHANTABILITY or FIT‐
NESS FOR A PARTICULAR PURPOSE.
SEE ALSOfsc(1), scalac(1), scaladoc(1), scalap(1)version 0.5 April 2007 scala(1)
