Scala scripting

Baldur Norddahl schrieb:
> find . -name '*.class' | scala -e "in.toStream.map{ x => x.replace('/','.').substring(2,x.lastIndexOf(\".\"))}.foreach(println _)"
>
> There is readline but it will only read one line at a time. It requires
> far too much boilerplate to create a stream of input lines to be useable
> together with the -e option. Any ideas on how to do this?

Not exactly pretty, but less than twice the length of your idea:

find . -name '*.class' | scala -e "var x : String = _; while({x = readLine; x != null}) { println(x.replace('/','.').substring(2,x.lastIndexOf(\".\")))}"

But a library of shell scripting primitives would be nice here, allowing something like

scala -cp Shell.jar -e "Cwd.find(Name('*.class')).map{ x => x.replace('/','.').substring(2,x.lastIndexOf(\".\"))}.foreach(println _)"

A source for inspriation could be http://www.scsh.net/

- Florian

> In general I feel Scala needs a larger toolset to be a better
> scripting option.

+1 !!

Perhaps PowerShell could be used for some inspiration.

2009/7/13 Detering Dirk :
>> In general I feel Scala needs a larger toolset to be a better
>> scripting option.
>
> +1 !!
>

Hi,

I am experimenting with using Scala instead of gawk or perl for simple commandline scripting. Currently I have this simple script:

find . -name '*.class' | xargs -n 1000 scala -e "argv.toList.map{ x => x.replace('/','.').substring(2,x.lastIndexOf(\".\"))}.foreach(println _)"

This finds all classes in an unpacked jar file and prints them in standard java form. For example "./com/sun/org/apache/xpath/internal/axes/FilterExprWalker.class" becomes "com.sun.org.apache.xpath.internal.axes.FilterExprWalker".

While this worked perfectly, there are two issues I am not 100% satisfied with.

1) change xargs -n1000 to xargs -n1 and this never completes (for rt.jar). Startup is order of magnitutes too slow. Perhabs there are no easy solutions, but I could wish for a simple command line parameter that would make scala cache the compiled script. When used together with -e it could hash the script into a temp filename for caching.

2) I want to get rid of the xargs. Maybe there already is a way but I can't find it. I want to do something like this:

find . -name '*.class' | scala -e "in.toStream.map{ x => x.replace('/','.').substring(2,x.lastIndexOf(\".\"))}.foreach(println _)"

There is readline but it will only read one line at a time. It requires far too much boilerplate to create a stream of input lines to be useable together with the -e option. Any ideas on how to do this?

In general I feel Scala needs a larger toolset to be a better scripting option.

Thanks,

Baldur

Scala will never be competitive on startup-time. Maybe on .Net, but, even then, I doubt it.   And, yes, a scala.shell library would be much welcome. If nothing else, replacing a whole shell script with Scala instead of just part of it would overcome the startup-time disadvantage.

On Sun, Jul 12, 2009 at 11:09 PM, Baldur Norddahl <baldur.norddahl@gmail.com> wrote:

Hi,

I am experimenting with using Scala instead of gawk or perl for simple commandline scripting. Currently I have this simple script:

find . -name '*.class' | xargs -n 1000 scala -e "argv.toList.map{ x => x.replace('/','.').substring(2,x.lastIndexOf(\".\"))}.foreach(println _)"

This finds all classes in an unpacked jar file and prints them in standard java form. For example "./com/sun/org/apache/xpath/internal/axes/FilterExprWalker.class" becomes "com.sun.org.apache.xpath.internal.axes.FilterExprWalker".

While this worked perfectly, there are two issues I am not 100% satisfied with.

1) change xargs -n1000 to xargs -n1 and this never completes (for rt.jar). Startup is order of magnitutes too slow. Perhabs there are no easy solutions, but I could wish for a simple command line parameter that would make scala cache the compiled script. When used together with -e it could hash the script into a temp filename for caching.

2) I want to get rid of the xargs. Maybe there already is a way but I can't find it. I want to do something like this:

find . -name '*.class' | scala -e "in.toStream.map{ x => x.replace('/','.').substring(2,x.lastIndexOf(\".\"))}.foreach(println _)"

There is readline but it will only read one line at a time. It requires far too much boilerplate to create a stream of input lines to be useable together with the -e option. Any ideas on how to do this?

In general I feel Scala needs a larger toolset to be a better scripting option.

Thanks,

Baldur

--
Daniel C. Sobral

Something I learned in academia: there are three kinds of academic reviews: review by name, review by reference and review by value.

Scala will never be competitive on startup-time. Maybe on .Net, but, even then, I doubt it.