#!/sw/bin/python
#               The "pound-bang" hack. Edit to put in 
#               your system's full path to python.
#               Type "which python" at the command line
#               to find out the path, if you don't know it.
#
#               Do a "chmod u+x" on this script to
#               make it executable, then you will be
#               able to execute it by just typing
#               it's name at the command line.
#
#
# This program reads a text file, and alters the
# newline tag as follows:
#     If it is a Mac file (\r) it turns it to Unix (\n)
#     If it is a Unix file (\n) it turns it to Mac (\r)
#     If it is DOS, (\r\n) it turns it to Unix
#     If it has a mixture of \r and \n it transforms to Unix
#
#   The following import allows us to get at command line arguments
#   sys.argv is a list of the arguments entered on the command line,
#   with sys.argv[0] always being the script name, even if the
#   user entered no arguments.
#
import sys
# Check if a file was specified on the command line
if len(sys.argv) <=1:
  InFileName = raw_input("Please specify a file to process:")
#         This illustrates the use of "raw_input()" to prompt
#         the user to enter some data. It is done here only if
#         the user didn't enter an input file name on the command 
#         line.
else:
  InFileName = sys.argv[1]
#
#   Build the output file name, or take it from the
#   second argument, if it's there.
#
if len(sys.argv) >=3:
  OutFileName = sys.argv[2]
else:
  OutFileName = InFileName+".crfix"
#  Note:  Should do something smarter with retaining the
#  extension of the infile name, if it's there.
#
#  Open the input file and read the whole thing into a buffer
#  If it's a big file, you might want to replace this with
#  a loop, reading in and processing one line at a time using 
#  readline() instead.
#
infile = open(InFileName,"r")
buff = infile.read()
infile.close()
#
#
#     Now check what kind of newline character is used,
#   and process the file accordingly.  Here we use
#   buff.find(...) which returns the index of the first
#   occurrence of the argument, or -1 if the argument
#   doesn't occur in the string.  Note that the string
#   buff is an object, and find is a method belonging
#   to it.
#     Instead of find(...), we could use count(...) which
#   counts the number of occurences.  Note also it might
#   be nice to check to make sure that the newline character
#   is used consistently throughout (i.e. no mixed Mac and Unix
#   newlines).
#
#      Note that replace(...) returns a new string which
#   is transformed as indicated. Below, we just overwrite the
#   old string with the new string, but you could save the
#   old one if you need to.
if buff.find('\r\n') > -1 :
   buff = buff.replace('\r\n','\n') #Turn DOS to unix
   print "DOS file changed to Unix file ",OutFileName
elif buff.find('\r') > -1 :
   buff = buff.replace('\r','\n')
   print "Mac file changed to Unix file ",OutFileName
elif buff.find('\n') > -1 :
   buff = buff.replace('\n','\r')
   print "Unix file changed to Mac file ",OutFileName
#
# The file has been transformed. Now write it out
#     (to be completely safe, we ought to check if
#     OutFileName already exists, and ask first before
#     overwriting if it does)
#
outfile = open(OutFileName,"w")
outfile.write(buff)
outfile.close()