Mercurial: The Definitive Guide

Case Sensitivity

If you’re working in a mixed development environment that contains both Linux (or other Unix) systems and Macs or Windows systems, you should keep in the back of your mind the knowledge that they treat the case (“N” versus “n”) of filenames in incompatible ways. This is not very likely to affect you, and it’s easy to deal with if it does, but it could surprise you if you don’t know about it.

Operating systems and filesystems differ in the way they handle the case of characters in file and directory names. There are three common ways to handle case in names:

• Completely case insensitive. Uppercase and lowercase versions of a letter are treated as identical, both when creating a file and during subsequent accesses. This is common on older DOS-based systems.

• Case preserving, but insensitive. When a file or directory is created, the case of its name is stored, and can be retrieved and displayed by the operating system. When an existing file is being looked up, its case is ignored. This is the standard arrangement on Windows and Mac OS. The names foo and FoO identify the same file. This treatment of uppercase and lowercase letters as interchangeable is also referred to as case folding.

• Case sensitive. The case in a name is significant at all times. The names foo and FoO identify different files. This is the way Linux and Unix systems normally work.

On Unix-like systems, it is possible to have any or all of the above ways of handling case in action at once. For example, if ...