Wednesday, August 24, 2011

Cygwin, Git Bash and native Windows apps, howto

I use Debian and Windows XP — the latter sometimes on a netbook, but principally on a fast desktop computer (it has a nice monitor). On Debian, I develop software in the normal way. But, when I'm on Windows, I have to resort to a variety of techniques.

On a fast desktop computer, I use many native Windows apps (e.g. 7-Zip instead of Tar with compression; in the Windows way). I use Cygwin apps where a good native Windows version is lacking.

For example, previously I ran Cygwin's LilyPond till I noticed the niceness of the Windows version.

But mostly on Cygwin I enjoy the Bash command line interface and its filesystem.

My desktop's Git is through Cygwin, but the netbook has msysGit (with its own version of Bash). (Msysgit is also known as Git Bash.)

Within msysGit, so far, Bash's symbolic links aren't good — if you make one, it actually copies the whole folder!

I could try alternatives (suggested on MinGW's MSYS page) such as Interix (also known as Microsoft's SFU or SUA).


In order to maintain only one copy on the desktop of things like SSH keys (used by Git) I followed instructions to move my Cygwin user home directory to the same place as my Windows user home directory — which worked just fine! (Additionally, I set LANG to en_US.UTF-8, as suggested.)

Now, this command works just fine for me:

ruby app/hello.rb

I seem to recall that, for a while, it gave me an error, 'no such file'. Perhaps when I cleaned and upgraded my Cygwin installation (including my .bash* files) and then did a couple of reboots, the problem went away. (Don't you hate that?)

Cygwin can run both Cygwin apps, and native Windows apps. For speed and maintainability reasons, it's good to minimize the programs installed into Cygwin, doing so only if no native Windows version will succeed there (or can conveniently be run outside it). For example, my RubyGems installation is a native Windows one.

In Cygwin, the command, 'rake' (e.g.) might give you:

No such file or directory -- /cygdrive/c/progra/ruby/1.8.7-p352/bin/rake (LoadError)

even though it is found by, 'which rake':


The solution (in Cygwin) is to type, 'rake.bat' (gem.bat, irb.bat, pik.bat, etc.).

If desired, you can alias rake, gem, irb and pik as with Robert Wahler's Stack Overflow answer, but just on the command line — it doesn't normally work in Bash scripts. (E.g., 'alias rake=rake.bat' — to reverse it: 'unalias rake'.)

If you are having problems with native Windows programs still not finding files in Cygwin, you might want to look at one aspect of Cygwin filesystems (some sources say) which requires special handling.

The documentation says passing filesystem paths (in Cygwin Bash) to native Windows apps (such as Ruby) is done (although sometimes I need to) in one of two ways:

One is to use native 'Win32' paths — two examples follow, for which I made a Ruby test program ('app/hello.rb' containing only, 'p __FILE__'). They require at least one, escaped backslash:

In (Cygwin's) current directory (using native Win32 paths):

ruby '.\hello.rb'
ruby .\\hello.rb

Or in 'app', relative to the current directory:

ruby 'app\hello.rb'
ruby app\\hello.rb

The other is to use cygpath:

In the current directory (add, '-a' for the full path):

ruby "`cygpath -m hello.rb`"

Or in the relative directory, 'app' (recently, with one long path, I had to do it this way):

ruby "`cygpath -m app/hello.rb`"


Developing with both msysGit and Cygwin normally generates Unix permissions problems. Their Gits flip-flop the permission bits between '100777' (Cygwin) and '100644' (msysGit) on most files! Those with certain typically-executable extensions like .exe and .bat alternate between '100777' (Cygwin) and '100755' (msysGit).

To avoid most of this problem, you can mount your Cygwin user home directory in a way close to the msysGit method:

/cygdrive/c/Documents\040and\040Settings/[user name] /home/[user name] ntfs binary,noacl,bind 0 0

'noacl' tells Cygwin not to use the Access Control Lists found in Microsoft's NT tree. (BTW, as of Cygwin 1.7.9-1, 'posix=1' and 'nouser' are ignored here.)

The exception is that Cygwin will look for '#!' at the beginning of files to set the executable bit; msysGit, as mentioned above, will look at extensions like .exe and .bat.

In a development project, it might be useful to set write- and execute-permissions (at least the 'user' bits). If you want to manipulate permission bits further in your repository, you can tell msysGit (or even Cygwin Git) to ignore permission bit differences. Then you can set (see Jakub Narębski's answer) the (user?) execute bits:

git update-index --chmod=+x [file paths]

and reset them:

git update-index --chmod=-x [file paths]

before you do, 'git commit'.

(Tested with Ruby 1.8.7 (2011-06-30 patchlevel 352) [i386-mingw32], Cygwin 1.7.9-1.)

BTW, to see what Cygwin version you are running:

cygcheck -c cygwin


file modes - Cygwin
NT Security - Cygwin
file modes - msysGit

Copyright (c) 2011, 2015 Mark D. Blackwell.

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