I was wondering how to make a python script portable to both linux and windows?
One problem I see is shebang. How to write the shebang so that the script can be run on
Windows will just ignore the shebang (which is, after all, a comment); in Windows you need to associate the .py
extension to the Python executable in the registry, but you can perfectly well leave the shebang on, it will be perfectly innocuous there.
There are many bits and pieces which are platform-specific (many only exist on Unix, msvcrt
only on Windows) so if you want to be portable you should abstain from those; some are subtly different (such as the detailed precise behavior of subprocess.Popen
or mmap
) -- it's all pretty advanced stuff and the docs will guide you there. If you're executing (via subprocess
or otherwise) external commands you'd better make sure they exist on both platforms, of course, or check what platform you're in and use different external commands in each case.
Remember to always use /
, not \
, as path separator (forward slash works in both platforms, backwards slash is windows-only), and be meticulous as to whether each file you're opening is binary or text.
I think that's about it...
I don't know enough to comment on Python approaches to this problem, so I won't.
Most things in Perl will just work. There are a few gotchas that are easy to avoid.
Here are a few things I have come across in the years I've been working with Win32 Perl:
open
. The two argument form can have problems with spaces in paths. (You should already be doing this anyway.)use Warnings;
will appear to work, but in reality it will fail.select
only works on actual sockets under Windows. You can't use it on any other sort of handle.File::Spec
to manage paths to files.CRLF
will automatically be converted to LF
line endings as the handle is read. LF
is changed to CRLF
on write. If you want to avoid this, use binmode
on the handle to prevent the translation.See perlport for more information on individual functions.
Make sure you don't handle files and directories as strings and simply concatenate them with a slash in between. Perl:
$path = File::Spec->catfile("dir1", "dir2", "file")
Remember that Windows has volumes:
($volume, $path, $file) = File::Spec->splitpath($full_path);
@directories = File::Spec->splitdir($path);
When running other programs, try to avoid involving the shell. In Perl, when you run a command with the system
function, you can easily get it wrong with:
$full_command = 'C:\Documents and Settings/program.exe "arg1" arg2'; # spaces alert!
system($full_command);
Instead, you can run system with a list as argument: the executable and the arguments being separate strings. In that case, the shell doesn't get involved and you don't get into trouble regarding shell escaping or spaces in file names.
system('C:\Documents and Settings/program.exe', 'arg1', 'arg2');
There's a bunch of portability nits documented in the perlport manual.
The shebang line will be interpreted as a comment by Perl or Python. The only thing that assigns it a special meaning is the UNIX/Linux shell; it gets ignored on Windows. The way Windows knows which interpreter to use to run the file is through the file associations in the registry, a different mechanism altogether.