All Tcl commands and C procedures that take file names as arguments expect the file names to be in one of three forms, depending on the current platform. However, scripts that are intended to be portable should not assume a particular form for file names. Absolute names are completely qualified, giving a path to the file relative to a particular volume and the root directory on that volume.
Relative names are unqualified, giving a path to the file relative to the current working directory.
The file pathtype command can be used to determine the type of a given path. Tcl supports two forms of path names. The normal Mac style names use colons as path separators. Paths may be relative or absolute, and file names may contain any char- acter other than colon. A leading colon causes the rest of the path to be interpreted relative to the current directory.