The problem

On Gentry, enter:

wget http://it.metr.ou.edu/dos2unix/fromwindows.zip

unzip fromwindows.zip

and out pops fromwindows.py. Then,

cat fromwindows.py

reveals:

#!/usr/bin/env python
#this was made using Notepad in Windows
print "Good morning starshine, I'm from Windows!"

You can probably figure out what the program is intended to do. You probably think you know what you need to do to make the program executable. But you might find that the s.o.b. thing just doesn't work. On Gentry you will get an error:

: No such file or directory

The problem is that in DOS/windows files, lines are ended with both a carriage return and a linefeed (python's "\r" and "\n", ascii \015 and \012) while unix uses just a linefeed character. If you do

cat -ve fromwindows.py

you will see all the "\r" rendered with a ^M, and all the "\n" with a $:

#!/usr/bin/env python^M$
#this was made using Notepad in Windows^M$
print "Good morning starshine, I'm from Windows!"^M$

The solution

dos2unix fromwindows.py
cat -ve fromwindows.py

The pesky ^M should be gone and the "killer app" fromwindows.py will be ready to go.

cat -ve fromwindows.py | head