On Unix and Apple MacOS X platforms, Tcl uses path names where the
components are separated by slashes. Path names may be relative or
absolute, and file names may contain any character other than slash.
The file names . and .. are special and refer to the
current directory and the parent of the current directory respectively.
Multiple adjacent slash characters are interpreted as a single
separator. Any number of trailing slash characters at the end of a
path are simply ignored, so the paths foo, foo/ and
foo// are all identical, and in particular foo/ does not
necessarily mean a directory is being referred.
The following examples illustrate various forms of path names:
On Microsoft Windows platforms, Tcl supports both drive-relative and UNC
style names. Both / and \ may be used as directory separators
in either type of name. Drive-relative names consist of an optional drive
specifier followed by an absolute or relative path. UNC paths follow the
general form \\servername\sharename\path\file, but must at
the very least contain the server and share components, i.e.
\\servername\sharename. In both forms,
the file names . and .. are special and refer to the current
directory and the parent of the current directory respectively. The
following examples illustrate various forms of path names:
In addition to the file name rules described above, Tcl also supports csh-style tilde substitution. If a file name starts with a tilde, then the file name will be interpreted as if the first element is replaced with the location of the home directory for the given user. If the tilde is followed immediately by a separator, then the $HOME environment variable is substituted. Otherwise the characters between the tilde and the next separator are taken as a user name, which is used to retrieve the users home directory for substitution. This works on Unix, MacOS X and Windows (except very old releases).
Old Windows platforms do not support tilde substitution when a user name follows the tilde. On these platforms, attempts to use a tilde followed by a user name will generate an error that the user does not exist when Tcl attempts to interpret that part of the path or otherwise access the file. The behaviour of these paths when not trying to interpret them is the same as on Unix. File names that have a tilde without a user name will be correctly substituted using the $HOME environment variable, just like for Unix.
Not all file systems are case sensitive, so scripts should avoid code that depends on the case of characters in a file name. In addition, the character sets allowed on different devices may differ, so scripts should choose file names that do not contain special characters like: <>:?"/\|. The safest approach is to use names consisting of alphanumeric characters only. Care should be taken with filenames which contain spaces (common on Windows systems) and filenames where the backslash is the directory separator (Windows native path names). Also Windows 3.1 only supports file names with a root of no more than 8 characters and an extension of no more than 3 characters.
On Windows platforms there are file and path length restrictions. Complete paths or filenames longer than about 260 characters will lead to errors in most file operations.
Another Windows peculiarity is that any number of trailing dots . in filenames are totally ignored, so, for example, attempts to create a file or directory with a name foo. will result in the creation of a file/directory with name foo. This fact is reflected in the results of file normalize. Furthermore, a file name consisting only of dots ......... or dots with trailing characters .....abc is illegal.
current directory, absolute file name, relative file name, volume-relative file name, portability