Richard's Cygwin Tips

Cygwin is a free Unix/Linux-like (POSIX) environment for Windows. It consists of:

• a DLL (cygwin1.dll) which acts as a Linux API emulation layer
• a collection of programs, config files, documentation, etc., providing a Linux look-and-feel

The official Cygwin home page is http://cygwin.com/.

Why Cygwin

• The MS-DOS/Windows console and command line shell is almost useless, there are few available console programs (with very ad hoc behaviour), and there is no package management.
• The Unix world has much better consoles and shells, loads of standardized and very useful programs, and the Cygwin installer program handles downloads and updates for you.

How does it work?

• It is not an emulator or virtual machine - the programs are normal Win32 executables that just use the Cygwin DLL.
• The whole point of the Cygwin DLL is that programs written for Unix/Linux don't have to be rewritten in order to run under Windows.
• This means that huge amounts of free/open source Unix software is available also on Windows.
• However, the programs believe that they are running in a Unix environment!
  • By default, they assume that newlines are LF, not CRLF, but this is usually not a problem (see the Cygwin FAQ entry on the CR/LF issue for further info.
  • For programs that are sensitive to newline conventions, you should keep DOS/Windows files separate from Cygwin/Unix files.
  • You can use the dos2unix and unix2dos commands to convert or normalize newlines in files.
• The programs see the Windows file system as if it was a Unix file system, with Unix user/group permissions, etc.
  • A Unix program compiled under Cygwin does not have to understand MS-DOS drive letters.  Instead of "C:\...", it just sees a normal Unix-like path "/cygdrive/c/...".
  • You can use the cygpath command in scripts to convert between Unix- and Windows-style paths.

Installing Cygwin

1. Go to http://cygwin.com and download the file setup.exe
2. Save this file somewhere for future use and make a shortcut to it. You will run it later every time you want to update or add packages.\
3. Run the setup.exe program once, without changing any settings (except for possibly the install directory). Keep all RECOMMENDED settings and don't add or remove packages yet.
   • ftp.sunet.se is a good mirror if you're in Sweden.
   • Detailed setup help can be found here
4. After installation, click one of the new icons to start a shell and check that things are working.
5. Whenever you want to check for updates, just run the setup.exe program again (without changing any settings). If there are updated versions of packages you already have, they will be automatically installed.
6. If you want to add or remove packages, do the same thing, but browse the package tree and select/deselect packages as you like.

Post-install setup

When you click the icon to start a Cygwin shell, it runs C:\Cygwin\cygwin.bat (if you used C:\Cygwin as the install directory). You should edit this file to set up some things:

1. Set the CYGWIN environment variable to "ntsec" (if you have NTFS partitions). Look here for more details.
2. Set the HOME environment variable to the DOS path to your home directory. If you used C:\Cygwin as install directory, then HOME is typically C:\Cygwin\home\username, but there is nothing stopping you from changing this to somewhere else.
3. You might want to specialize your PATH settings for Cygwin shells. For example:
    set CYGWIN=ntsec
    set HOME=C:\Cygwin\home\Dorothy\

Caveats

• Many "plain Windows" console programs don't work properly with input if they are called from a Cygwin-shell; in particular, programs that want to ask the user questions about password etc. tend to hang or not print the question until you have pressed enter. There is more details on this problem in the PuttyCyg FAQ.
• Because of package dependencies, you may get Cygwin-versions of languages like Perl, Python, Ruby, etc., that you might already have native Windows versions of. It can be tricky to make sure that you run the right version at the right time. In general, don't try to run the Windows versions of such languages from the Cygwin shell, but run them from a normal Windows console instead.
• Although you might think it would be convenient to have access to Cygwin utilities even when you're not in a Cygwin shell, by putting C:/cygwin/bin in your global Windows PATH, this may cause DLL conflicts where there are two types of DLLs with the same name (tcl84.dll is a common example), or just get you into trouble with having both a Cygwin executable and a Windows executable with the same name (find.exe is one example). The general advice is do not put cygwin/bin in your Windows PATH! Use GnuWin32 to get the most common Unix tools as native Windows programs instead, and put those in your Windows path.

A better console window

By default, Cygwin will use the standard Windows console to run the command line interpreter in. Since this sucks in many ways, you should use rxtv instead.

Rxvt

1. Run setup.exe again, and just skip to package selection. In the group shells, you should find rxvt: "VT102 terminal emulator for both X and Windows". Select this, and click Next to finish the installation.

2. Edit C:\Cygwin\cygwin.bat again, and change the line that starts bash (or whatever shell you use) to the following:

   rxvt -e bash --login -i

The thing with rxvt is that it is really an X11 application, but it also works on Windows without an X11 server running. Either way, you can configure it in your $HOME/.Xresources file; e.g., like this:

rxvt.geometry: 80x32 rxvt.boldFont: Lucida Console-12 rxvt.font: Lucida Console-12 rxvt.loginShell: True rxvt.saveLines: 5000 rxvt.scrollBar_right: True rxvt.visualBell: True

Configuring tab-completion etc.

The shell (bash) uses the GNU Readline library to read lines of input. This is where the input history, tab-completion, etc., is handled. You can configure it by editing your $HOME/.inputrc file. Here is an example:

# These are for proper 8-bit characters (åäö, etc.) set meta-flag on set input-meta on set output-meta on set convert-meta off

# Just flash screen, don't beep set bell-style visible

# Be case-insensitive (nice on Windows machines) set completion-ignore-case on

# These are also nice for tab-completion set completion-query-items 16 set mark-symlinked-directories on set print-completions-horizontally on set show-all-if-unmodified on

# Home Key "\e[7~":beginning-of-line

# End Key "\e[8~":end-of-line

# Ctrl-cursor right/left # (change to end-of-line/beginning-of-line if you prefer) "\eOc":forward-word "\eOd":backward-word

# Alt-cursor right/left "\e\e[C":forward-word "\e\e[D":backward-word

# Page up/down for beginning/end of history "\e[5~":beginning-of-history "\e[6~":end-of-history

Run "man readline" for details and more options. An easy way of checking the control sequence generated by a keypress is to run the command "od -c" and type away. End by pressing Ctrl-d twice. Where the output says "033", use "\e" in the file.

Starting an X server

An X server is useful for running GUI programs on remote Unix machines, but have the windows pop up on your local screen instead.

First, you need to run the Cygwin setup.exe program and install at least the package xorg-x11-base (in the package group X11). See here for detailed help.

After installation, the easiest way to start the X server is probably by creating a shortcut to the file C:\Cygwin\usr\X11R6\bin\startxwin.bat. You shouldn't need to edit the .bat file, but you might want to take a look at it just to see what it is doing. More details here.

Note that when the server is running, you can control it through an icon in the Windows tray.