[Jython-users] Aargh! Jython and Readline

[Steve C. <St...@ig...>]

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the documentation is out of date.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.

After all that, you finally have a console that recognizes the arrow
keys for history when on the last line.  Way too complicated. =20

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.