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Re: Practical method for automatic Cygwin install?

On Tue, Nov 22, 2005 at 09:51:56PM -0600, William J. Leslie wrote:
>Note: I am rephrasing the question I asked last time (for which the
>conversation drifted into GPL and licensing issues).
>My program depends on cygwin DLLs, my installer must make sure these
>dependencies are satisfied.  I've heard that installing private copies of
>cygwin DLLs can lead to version mismatches. Instead of installing private
>copies of the cygwin DLLs, my installer will install a complete (but minimal)
>cygwin installation to c:\cygwin.
>There are a few issues that I am not sure how to deal with:
>1) How to determine whether or not cygwin is already installed? If so, what
>is the prefix path (e.g. c:\cygwin)?

Right now, the only way to do it is to query the registry.  I think I'm
convinced that cygwin will always need to add something to the registry
so the concept of querying the registry to find out if cygwin is
installed should be useful for the foreseeable future, even if the
location to query might change (and what a hue and cry there will be if
it does change).

It is possible to copy the cygwin DLL to a system and just have it work,
though, so what I would do is:

0) Look at the current installer to see how it does things.

1) Try running "mount --version" to see if it is the cygwin version.  If it
succeeds and the word "cygwin" shows up in the output, then cygwin is installed.
This assumes that mount is in the path.

2) Look in the registry (in the currently used location) for the cygwin
root directory.  See if the bin directory under this location contains
cygwin1.dll.  If it succeeds, then cygwin is installed.

>2) If cygwin is already installed, what optional packages are present? What

Use the same method as the current setup (and cygcheck) to determine
what packages are installed.

>3) If cygwin is NOT installed, how do we install it, without setup.exe
>prompts?  (I have a gut feeling that it's a bit more complicated than just
>untarring packages.)

It's not a lot more complicated than that.  You have to get dependencies
right and you have to deal with post install scripts.

>4) If cygwin is installed, but some optional packages need version upgrades,
>how do we accomplish that?

As Gary said in another message, it sounds like the best way to
accomplish what you want is to augment setup.exe and make sure that your
changes show up in the official version.  You contribute to setup.exe
via the cygwin-apps mailing list.  Maybe you might want to peruse the
archives of that mailing list to see how that happens.


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