Re: [Jython-users] Aargh! Jython and Readline

[<bc...@wo...>]

[Steve Cohen]

>For about the third time, I have spent a few hours getting the readline
>library worked into jython.  (It happens every time I install a new
>jython and it changes a little bit each time.) You would think this
>annoying mess would get documented somewhere, but it hasn't, anywhere,
>correctly, in spite of several halfway attempts to do so.  And much of
>the documentation is out of date.
>
>So please, guys, make it a New Year's resolution to get this into the
>official docs, somewhere.  Here is a start, it worked for me:
>
>
>What you have to do to get Jython and Readline working (These
>instructions work for GNUReadline on my RedHat Linux system - your
>mileage may vary):=20
>
>Note: there is another option called Editline but Bernhard Bablok, the
>author of gnu java_readline says he couldn't get it working, so I didn't
>even try.  Nonetheless, Editline is the default in jython according to
>the source code in ReadlineConsole.java.  (See item #9 below ) If this
>is going to be the case, then the jython docs should give more info
>about it or work it into the standard distribution somehow. =20
>
>1.  Download and install the javacc from
>http://www.webgain.com/products/java_cc/.  You can't build jython
>without this.
>
>2.  Download the java-readline source from
>http://www.bablokb.de/java/readline.html
>
>3.  Make the java_readline jar and backing library using the Makefile
>supplied.=20
>
>4.  Deploy these into your system lib directory.  (/usr/lib in my case)
>
>5.  Download the latest Jython sources from SourceForge. =20
>
>6.  Create/Modify an ant.properties file in the same directory as the
>build.xml for jython and add the property readline.jar giving it the
>value of a path to the java_readline.jar you deployed in step 3,  as
>well as the path to javacc and any other optional jars you wish to
>include.
>
>7.  Build jython and deploy it.
>
>8.  Modify the jython shell script so as to precede the supplied command
>(java -Dpython.home=3D...) with 'LD_LIBRARY_PATH=3D"/usr/lib"'
>
>9.  Modify your registry file to add the line
>
>     python.console.readlinelib=3DGnuReadline
>
>As far as I know this one isn't documented anywhere and if you don't put
>it in, the system tries to find Editline and throws an exception if it
>can't. I only pieced it together from reading the source code for
>jython's ReadlineConsole and for the gnu java readline.

I think you have made it more difficult than you have to. To enable
readline you can use the binary distribution of jython-21b2, you just
have to set the registry options:

    python.console=org.python.util.ReadlineConsole
    python.console.readlinelib=GnuReadline

You still have to do items 2, 3, 4, 5 and 8, but I would rather not have
to document how because I have truely no clue about it.

The documentation for item 9 was missing, I have added a note about
python.console.readlinelib to the registry.html web-page.

    http://www.jython.org/docs/registry.html

Thank you for reporting the missing doc.

>After all that, you finally have a console that recognizes the arrow
>keys for history when on the last line.  Way too complicated.
>
>So while I thank the Jython developers and Mr. Bablok for their efforts
>and for making this possible at all, please, someone, make this easier
>or at least pull all the documentation into one place.

Sounds like a good candidate for a FAQ entry. Does anyone want to write
it up? The faqwizard is read-only at the moment but send the text to the
list, then I'll add it.

regards,
finn