Question

I’m working on a project that uses Jython 2.2.

Seems like Jython 2.2 doesn’t have os.symlink() or anything that can help create a symbolic link.

So I thought to use the Java createSymbolicLink(). But createSymbolicLink() requires a Java data type “Path”, which I have no clue about how to import into Jython…

Does anyone have any idea about how to create a symbolic link in Jython (preferably not using shell commands)?

P.S. I tried “createSymbolicLink()” with Java 1.6.0 and it didn’t work because somehow Java didn’t recognize “Path” even after I did “import java.nio.*”… Any idea…?

Thanks a lot!

Jack

Answer 1

There is no support for symlinks in Java 6. With Java 7 you could (untested):

from java.nio.file import FileSystems # requires Java 7 (July 28, 2011)

def mksymlink(target, path):
    """Make a symlink from target to path."""
    fs = FileSystems.getDefault()
    target, path = [fs.getPath('', [name]) for name in [target, path]]
    path.createSymbolicLink(target)

Jython 2.5 has os.symlink() implemented using jruby posix module.

With Jython 2.2 on Java 6 you might need to call ln:

import os
from java.lang import Runtime

def mksymlink(target, path):
    path = os.path.abspath(path)
    process = Runtime.getRuntime().exec(["ln", "-s", target, path]);
    process.waitFor();
    process.destroy();

To mass produce symlinks you could communicate with external python process:

import os
from java.lang import Runtime
from java.io import PrintWriter

class Symlinker:
    def __init__(self, path):
        self.process = Runtime.getRuntime().exec(path)
        self.out = PrintWriter(self.process.getOutputStream())

    def __call__(self, target, path):
        self.out.write("%s\0%s\n" % (target, path))
        self.out.flush()

    def terminate(self):
        self.out.close()
        self.process.waitFor()
        self.process.destroy()

symlinker = Symlinker(["python", "symlinker.py"])

def mksymlink(target, path):
    symlinker(*map(os.path.abspath, [target, path]))

Where symlinker.py:

#!/usr/bin/env python
import os, sys

for line in iter(sys.stdin.readline, ''):
    target, path = line.rstrip('\n').split('\0')
    os.symlink(target, path)

It is a translation to Jython/Python of Java/C implementation from Creating Symbolic Links with Java at Runtime.