# Cygwin Tips & Tricks

Some random hints …

Cygwin support two kinds of symlinks: emulated symlinks and native windows symlinks. The advantage of emulated symlinks is that they will work on all file systems and with all windows versions. And every user can create them. Therefore, these kinds of symlinks are created by default. The disadvantage is that they are only understood by cygwin based tools, not by native windows programs like the OCaml compiler. (ocambuild behaves particular strange. ocamlbuild will under certain conditions create symlinks with ln, but can’t deal with them later.)

If you have the necessary rights, you can instruct cygwin to always create native windows symlinks instead by setting a special environment variable (CYGWIN=winsymlinks:native). You can circumvent some problems this way.

## Bind mounts

Cygwin supports “bind mounts”, e.g:

While this is a nice feature, you should use it very carefully, if at all. When you use opam/OCaml from within cygwin, you frequently switch between native Windows programs (the OCaml compiler, ocamlfind, ocamlbuild) and cygwin tools (shell, git, c compiler). Only the latter can understand bind mounts.

If you are at ~/Downloads under cygwin, windows programs behave as if they were at C:/Users/MYUSERNAME/Download; the outputs of cmd.exe /c dir .. and ls -l .. will differ. Which location is meant by ../foo?

## Environment

Check your environment inside a cygwin terminal ($env). And then configure your ~/.bashrc to remove anything from the environment that you don’t really need inside cygwin. Remove especially unnecessary paths from $PATH. If your $PATH list is very long or contains network paths, this will have a negative performance impact. And of course, it can cause confusion for you or your scripts, if there is something in your$PATH which is named like a Unix-tool, but was installed long time ago by a dubious Windows-related installer.

## Terminal emulators

There are two kinds of terminal emulators:

1. Cygwin terminals, like mintty or rxvt-unicode.
2. “Native” windows terminals, like ConEmu or ConsoleZ.

You can configure the latter to start with cygwin’s bash (or zsh) instead of cmd.exe or powershell. Use whatever you like. However, some tools like utop will only work under “real” terminals, not the faked ones that are shipped by cygwin.

Both kinds of terminal emulators can be greatly enhanced, if you modify your .bashrc or .zshrc (rxvt-unicode can be configured by ~/.Xdefaults - as under linux). The default configurations are very minimalistic.

## Emacs

Again, you have several choices:

• the native windows version
• cygwin’s emacs inside mintty/rxvt-unicode
• cygwin’s emacs with a X11 interface (emacs-X11 inside cygwin’s setup_*.exe )
• cygwin’s emacs with a native windows gui (emacs-w32)

The problem with cywin’s emacs is, that this version can’t deal with windows paths (C:\foo\bar); and the native version can’t deal with cygwin’s path conventions (/home/user/file, /cygdrive/c/foo/bar). Windows paths are emitted by the OCaml compiler, cygwin paths by the mingw-w64 compiler :)

Whichever version you choose, you have to teach emacs about foreign paths, either with cygwin-mount.el or with windows-path.el. Consult the EmacsWiki for further information.