#! /usr/bin/env python2.4

"""Resolves symbolic links. "snl" = "ln -s" backwards.

Usage:

	snl [-s] [-r] <path1> <path2> ... <pathN>

For each path given on the command line, 

Flags:

	-s	suppress printing of paths which are not symlinks

	-1	only perform one round of resolution (by default, resolve all the
	way down)

"""

import sys
import getopt
import os

RECURSION_LIMIT = 100

def deepreadlink(path):
	"""Takes an absolute path and, if it or any of its parent 
	directories are links, returns the target of the link. If there are 
	no links to be had, returns None.
	
	"""
	if (os.path.islink(path)):
		return os.readlink(path)
	else:
		dir, name = os.path.split(path)
		assert (dir != ""), "attempt to read relative path: " + path
		if (dir == "/"):
			return None
		tgtdir = deepreadlink(dir)
		if (tgtdir == None):
			return None
		return os.path.join(tgtdir, name)

def resolve(path, recurse=True, recursionLimit=RECURSION_LIMIT):
	if (recursionLimit == 0):
		raise ValueError, "recursion limit exceeded at path: " + path
	if (not os.path.lexists(path)):
		raise ValueError, "path does not exist: " + path
	path = os.path.abspath(path)
	tgtpath = deepreadlink(path)
	if (tgtpath == None):
		return path
	if (tgtpath == path):
		raise ValueError, "self-referential link: " + path
	if (recurse):
		return resolve(tgtpath, True, (recursionLimit - 1))
	else:
		return tgtpath

def err(*msg):
	sys.stderr.write((" ".join(map(str, msg)) + "\n"))

if (__name__ == "__main__"):
	try:
		flags, args = getopt.gnu_getopt(sys.argv[1:], "s1")
		if (len(args) == 0): raise getopt.GetoptError, "no arguments supplied"
		suppress = ("-s", "") in flags
		recurse = ("-1", "") not in flags
		for path in args:
			try:
				rpath = resolve(path, recurse)
				if (suppress and (path == rpath)): continue
				print rpath
			except ValueError, e:
				err((path + ":"), e)
	except getopt.GetoptError, e:
		print "Error:", e
		print
		print __doc__