Die Ruhe Liegt Im Eichenhain

Windows does not offer an equivalent to Unix’ shebang, e.g. #!/usr/bin/perl -T, which is unfortunate. Instead, Windows users can register a default program with each file extension, that is invoked if the user double-clicks on a file or if a file is run from the Windows command prompt. This is less flexible because file-specific arguments to the invoked program, such as -T in my initial shebang example, cannot be stored alongside the file. Moreover, having to use a graphical interface to register programs with extensions doesn’t overly excite me.

However, since Windows 2000 there exists the – so far unknown to me – possibility of getting the task done via the shell utilities assoc and ftype:

Source code

$>assoc .scala=ScalaFile
.scala=ScalaFile
  
$>ftype ScalaFile=C:\Program Files\scala\bin\scala.bat -savecompiled %1 %*
ScalaFile=C:\Program Files\scala\bin\scala.bat -savecompiled %1 %*

This still is less flexible than the shebang, but, well … everybody needs something that he/she is looking forward to see implemented in his/her favourite operating system, right?

Thanks to the folks at ActiveState for pointing this out.

Imagine that you have a program foo.exe which takes multi-word command line arguments, for example

Source code

$>foo.exe aShortArg aKey:"multi-word arg"
arg1 = aShortArg
arg2 = aKey:"multi-word arg"

You also have a timing script timer.scala (could also be written in Java) which runs another program and measures its runtime. To facilitate starting the script you have written a batch file which runs the actual script.

Source code

// timer.bat
@echo off
SetLocal
 
set CP=.;%SCALA_HOME%\lib\scala-library.jar
set JAVA_OPTS=%JAVA_OPTS% -Xss16m
 
call java %JAVA_OPTS% -cp "%CP%" TimerMain %*

In order to not worry about properly escaping double quotes when passing them to timer.bat, .e.g

Source code

$>timer.bat bbb.exe path\to\aaa.exe aKey:"multi-word arg"
Starting benchmark ...
Running aaa.exe at path\to:
arg1 = aKey:multi-word
arg2 = arg
... DONE
Runtime: 1s
 
$>timer.bat bbb.exe path\to\aaa.exe aKey:"\"multi-word arg\""
Starting benchmark ...
Running aaa.exe at path\to:
arg1 = aKey:"multi-word arg"
... DONE
Runtime: 1s

you can change timer.bat such that double quotes get escaped automatically before they are forwarded:

Source code

// timer.bat
@echo on
SetLocal EnableDelayedExpansion
 
set ARGS=
 
:parse_args
if not %1.==. (
  set ARG=%1
  set ARGS=!ARGS! ^"!ARG:"=\"!^"
  shift
  goto :parse_args
)
 
set CP=.;%SCALA_HOME%\lib\scala-library.jar
set JAVA_OPTS=%JAVA_OPTS% -Xss16m
 
call java %JAVA_OPTS% -cp "%CP%" TimerMain %ARGS%

This also you to forget about escaping double quotes, and enables you to simply specify the arguments to foo as if they were direct arguments, i.e. as if they would not be looped through the timer script:

Source code

$>timer.bat bbb.exe path\to\aaa.exe aKey:"multi-word arg"
Starting benchmark ...
Running aaa.exe at path\to:
arg1 = aKey:"multi-word arg"
... DONE
Runtime: 1s