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Welcome to the fscala wiki!

Use Scala as a scripting language

See this blog entry and http://www.scala-lang.org/node/166 as examples of how and why to use Scala as a scripting language.

But the latency to start a Scala script is really high. The helloworld script (see examples/oldscala.scala takes as much as 8.5 seconds to run on a 2.66GHz Duo Core Linux box. fscala tries to eliminate unnecessary steps in running the scripts to reduce start time.

fscala User Guide

To use fscala, put it in your PATH, and make sure it is executable. Then in the first line of your scala script, write #!/usr/bin/env fscala, and make it executable too. That's it! You do not need !# to define the end of the script header. In fact if you have it then it won't compile. If you don't like to change your first line of the script, you can also run fscala your_script.scala.

There are two variables implicitly available in your script: argv and args. args is similar to Java's default args behavior. argv contains one extra element at the head which is the path to the script itself, i.e. $0 $1 ... $n. This is closer to the argv in other scripting language, e.g. Python. You can ignore them and redefine to whatever you like. See examples/hello3.scala as an example.

What fscala does is very simple. Suppose your script is named hello.scala. fscala will wrap hello.scala into an object called ScriptMain, write the new source file into .hello.classes/hello.scala. Then it calls fsc to compile the file. If the compiled class file is newer than hello.scala, compilation is skipped. Finally it calls java with the correct classpath to launch your script. fscala is faster than the -savecompiled option with scala for around 0.1-0.3 seconds.

Performance

Here we compare the performance of a very simple hello world script in both fscala and scala with the -savecompiled option. The two test scripts hello1.scala and oldscala.scala can be found in examples/.

Case 1: fsc server has started. The script needs to be recompiled.

fscala

$ touch hello1.scala && time ./hello1.scala 
Hello, world, from a script! List()
real    0m0.864s
user    0m0.610s
sys     0m0.090s

scala -savecompiled

$ touch oldscala.scala && time ./oldscala.scala 
Hello world, from a script! List()
real    0m1.371s
user    0m0.710s
sys     0m0.040s

Case 2: the script is compiled already.

fscala

$ time ./hello1.scala 
Hello, world, from a script! List()
real    0m0.217s
user    0m0.270s
sys     0m0.020s

scala -savecompiled

$ time ./oldscala.scala 
Hello world, from a script! List()
real    0m0.545s
user    0m0.600s
sys     0m0.060s