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scalac - Man Page

Compiler for the Scala 2 language


scalac  [ <options> ] <source files>



Command line options. See Options below.

<source files>

One or more source files to be compiled (such as MyClass.scala).


The scalac tool reads class and object definitions, written in the Scala programming language, and compiles them into bytecode class files.

By default, the compiler puts each class file in the same directory as its source file. You can specify a separate destination directory with -d (see Options, below).


The compiler has a set of standard options that are supported on the current development environment and will be supported in future releases. An additional set of non-standard options are specific to the current virtual machine implementation and are subject to change in the future.  Non-standard options begin with -X.

Standard Options


Pass -Dproperty=value  directly to the runtime system.


Pass <flag> directly to the runtime system.


Pass an option to a plugin


Print a synopsis of advanced options.

-bootclasspath <path>

Override location of bootstrap class files (where to find the standard built-in classes, such as "scala.List").

-classpath <path>

Specify where to find user class files (on Unix-based systems a colon-separated list of paths, on Windows-based systems, a semicolon-separated list of paths). This does not override the built-in ("boot") search path.

The default class path is the current directory. Setting the CLASSPATH variable or using the -classpath command-line option overrides that default, so if you want to include the current directory in the search path, you must include "." in the new settings.

-d <directory|jar>

Specify where to place generated class files.


Emit warning and location for usages of deprecated APIs.

Available since Scala version 2.2.1

-encoding <encoding>

Specify character encoding used by source files.

The default value is platform-specific (Linux: "UTF8", Windows: "Cp1252"). Executing the following code in the Scala REPL will return the default value on your system:

   scala> new java.io.InputStreamReader(System.in).getEncoding


Explain type errors in more detail.

-extdirs <dirs>

Override location of installed extensions.


Emit warning and location for usages of features that should be imported explicitly.


"none" generates no debugging info,

"source" generates only the source file attribute,

"line" generates source and line number information,

"vars" generates source, line number and local variable information,

"notailcalls" generates all of the above and will not perform tail call optimization.


Print a synopsis of standard options.

-javabootclasspath <path>

Override Java boot classpath.

-javaextdirs <path>

Override Java extdirs classpath.


Enable one or more language features.


Ignore @specialize annotations.


Do not use the boot classpath for the Scala jar files.


Generate no warnings


Generates faster bytecode by applying optimisations to the program.


Print program with all Scala-specific features removed.

-sourcepath <path>

Specify location(s) of source files.


"jvm-1.8" target JVM 1.8 (default)

-toolcp <path>

Add to the runner classpath.


Enable detailed unchecked (erasure) warnings

Non variable type-arguments in type patterns are unchecked since they are eliminated by erasure

Available since Scala version 2.3.0


Uniquely tag all identifiers in debugging output.


Utilize the java.class.path in classpath resolution.


Utilize the manifest in classpath resolution.


Output messages about what the compiler is doing


Print product version and exit.


A text file containing compiler arguments (options and source files)

Advanced Options


Wrap field accessors to throw an exception on uninitialized access.


Enable warnings for developers working on the Scala compiler


Generate no assertions and assumptions

-Xelide-below <n>

Calls to @elidable methods are omitted if method priority is lower than argument.


Fail the compilation if there are any warnings.


Retain pre 2.10 behavior of less aggressive truncation of least upper bounds.

-Xgenerate-phase-graph <file>

Generate the phase graphs (outputs .dot files) to fileX.dot.


Enable recommended additional warnings.


Print a message when reification creates a free term.


Print a message when reification resorts to generating a free type.


Print a message whenever an implicit conversion is inserted.


Print a message when a reflective method call is generated.


Custom settings for macros.

-Xmain-class <path>

Class for manifest's Main-Class entry (only useful with -d <jar>).


Warn about constructs whose behavior may have changed since<version>.


Do not generate static forwarders in mirror classes.


Don't perform exhaustivity/unreachability analysis. Also, ignore @switch annotation.


The JLine keybindings to use: emacs/vi/off.


Load a plugin from each classpath.


Disable plugins by name.


Print a synopsis of loaded plugins.


Abort if a named plugin is not loaded.

-Xpluginsdir <path>

Path to search for plugin archives.


Print out program after <phases> (see below).


Print tree positions, as offsets.


Print tree types (debugging option).


Display a prompt after each error (debugging option).


Compiler stays resident, files to compile are read from standard input.

-Xscript <object>

Treat the source file as a script and wrap it in a main method.

-Xshow-class <class>

Show internal representation of class.

-Xshow-object <object>

Show internal representation of object.


Print a synopsis of compiler phases.


Treat compiler input as Scala source for the specified version, see scala/bug#8126.

-Xsource-reader <classname>

Specify a custom method for reading source files.


Don't infer known-unsound types.


Verify generic signatures in generated bytecode (asm backend only).


Configure XML parsing.

"coalescing" convert PCData to Text and coalesce sibling nodes (default in 2.11).


Print a synopsis of private options.

Compilation Phases


parse source into ASTs, perform simple desugaring


resolve names, attach symbols to named trees


load package objects


the meat and potatoes: type the trees


translate match expressions


add super accessors in traits and nested classes


add extension methods for inline classes


serialize symbol tables


reference/override checking, translate nested objects


ANF pre-transform for @cps (CPS plugin)


@cps-driven transform of selectiveanf assignments (CPS plugin)


uncurry, translate function values to anonymous classes


replace tail calls by jumps


@specialized-driven class and method specialization


this refs to outer pointers, translate patterns


erase types, add interfaces for traits


clean up erased inline classes


synthesize accessors and fields, including bitmaps for lazy vals


move nested functions to top level


move field definitions into constructors


eliminate inner classes


mixin composition


platform-specific cleanups, generate reflective calls


remove lambdas


optimization: do inlining


optimization: inline exception handlers


optimization: eliminate uncalled closures


optimization: optimize null and other constants


optimization: eliminate dead code


generate JVM bytecode


the last phase in the compiler chain


matches all phases



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.


Specify JDK/JRE home directory. This directory is used to locate the java command unless JAVACMD variable set.


Specify the options to be passed to the java command defined by JAVACMD.

One might for example configure the memory usage of the JVM with: JAVA_OPTS="-Xmx2G -Xss16M"


Compile a Scala program to the current directory

scalac HelloWorld

Compile a Scala program to the destination directory classes

scalac -d classes HelloWorld.scala

Compile a Scala program using a user-defined java command

env JAVACMD=/usr/local/bin/cacao scalac -d classes HelloWorld.scala

Compile all Scala files found in the source directory src to the destination directory classes

scalac -d classes src/*.scala

Exit Status

scalac returns a zero exit status if it succeeds to compile the specified input files. Non zero is returned in case of failure.


Written by Martin Odersky and other members of the Scala team.

Reporting Bugs

Report bugs to https://github.com/scala/bug/issues.

See Also

fsc(1), scala(1), scaladoc(1), scalap(1)

Referenced By

fsc(1), scala(1), scaladoc(1), scalap(1).

March 2012 version 1.0 USER COMMANDS