Where can I download an offline installer of Cygwin?
Not a direct answer to your question, but you can get the most commonly used utilities from http://www.mingw.org/ without having to jump through the hoops with that horrible Cygwin installer.
Here is a slightly more informative link http://sourceforge.net/apps/mediawiki/cobcurses/index.php?title=Install-MSYS.
- Pick a mirror server closest to you from http://cygwin.com/mirrors.html
Choose any FTP or HTTP mirror.
Download the whole mirror maintaining exact file tree structure of the cygwin directory in the mirror.
Edit: How to download the whole mirror?
wget -m <ftp-mirror-url>Execute setup.exe & choose source as local directory and browse to the release directory.
Now you have the Offline Cygwin Installer.
Update: Use Babun. It's based on cygwin and more user friendly. Get Babun
Update 2: Use cmder with git for windows.
Here are instructions assuming you want to install Cygwin on a computer with no Internet connection. I assume that you have access to another computer with an Internet connection. Start on the connected computer:
Get the Cygwin install program ("setup.exe"). Direct download URL: x86 or x86_64.
When the setup asks "Choose a download source", choose Download Without Installing
Go through the rest of the setup (choose download directory, mirrors, software packages you want, etc)
Now you have a Cygwin repository right there on your hard disk. Copy this directory, along with the "setup.exe" program, over to your target computer (it does not need to be on a network).
On the target computer, run "setup.exe"
When the setup asks "Choose a download source", choose Install From Local Directory
Complete setup as usual. No Internet access is required.
If all you want is the UNIX command line tools I'd suggest not installing Cygwin. Cygwin wants to turn your Windows PC into a UNIX Workstation which is why it likes to install all its packages.
Have a look at GnuWin32 instead. It's Windows ports of the command line tools and nothing else. Here is the installer for the GnuWin32 diff.exe. There are offline installers for all the common tools.
(You asked for offline installers but in case you ever want one later there is a tool which will download and install everything for you.)
Method 2: make an offline install zip file for cygwin.
Don't mess with saving packages because the installed directory for cygwin can be canned in a zip file and expanded whenever you need it on any computer.
Download Cygwin installer
pick packages you want installed from gui.
hit install and wait a really long time for everything to download.
zip up the C:\Cygwin folder. Now you have your offline zip file for installing cygwin on any machine.
Unzip this file on whatever computer you like. set cmd.exe paths appropriately to point to cygwin bin directory under windows control panel.