Tcl Built-In Commands filename(1T)
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NAME
filename - File name conventions supported by Tcl commands
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INTRODUCTION 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. On each platform, Tclsupports file names in the standard forms(s) for that plat-
form. In addition, on all platforms, Tcl supports a Unix-
like syntax intended to provide a convenient way of con-
structing simple file names. However, scripts that are intended to be portable should not assume a particular form for file names. Instead, portable scripts must use the file split and file join commands to manipulate file names (see the file manual entry for more details). PATH TYPES File names are grouped into three general types based on thestarting point for the path used to specify the file: abso-
lute, relative, and volume-relative. 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 filerelative to the current working directory. Volume-relative
names are partially qualified, either giving the path rela-
tive to the root directory on the current volume, or rela-
tive to the current directory of the specified volume. The file pathtype command can be used to determine the type of a given path. PATH SYNTAX The rules for native names depend on the value reported inthe Tcl array element tcl_platform(platform):
mac On Apple Macintosh systems, Tcl supports two forms of path names. The normal Mac style names use colons as path separators. Paths may be relativeor 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. If a path contains a colon that is not at the beginning, then the path is interpreted as an absolute path. Sequences of two or more colons anywhere in the path are used to construct relative paths where :: refers to the parent of the current directory, ::: refers to the parent of the parent, and so forth. Tcl Last change: 7.5 1Tcl Built-In Commands filename(1T)
In addition to Macintosh style names, Tcl alsosupports a subset of Unix-like names. If a path
contains no colons, then it is interpreted like a Unix path. Slash is used as the path separator. The file name . refers to the current directory,and .. refers to the parent of the current direc-
tory. However, some names like / or /.. have no mapping, and are interpreted as Macintosh names. In general, commands that generate file names will return Macintosh style names, but commands that accept file names will take both Macintosh andUnix-style names.
The following examples illustrate various forms of path names: : Relative path to the current folder. MyFile Relative path to a file named MyFile in the current folder. MyDisk:MyFile Absolute path to a file named MyFile on the device named MyDisk. :MyDir:MyFile Relative path to a file name MyFile in a folder named MyDir in the current folder. ::MyFile Relative path to a file named MyFile in the folder above the current folder. :::MyFile Relative path to a file named MyFile in the folder two levels above the current folder./MyDisk/MyFile Absolute path to a file named MyFile on the device named MyDisk.
../MyFile Relative path to a file named MyFile in the folder above the current folder. unix On Unix 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. Tcl Last change: 7.5 2
Tcl Built-In Commands filename(1T)
The following examples illustrate various forms of path names:/ Absolute path to the root direc-
tory. /etc/passwd Absolute path to the file named passwd in the directory etc in the root directory.. Relative path to the current direc-
tory. foo Relative path to the file foo in the current directory. foo/bar Relative path to the file bar in the directory foo in the current directory. ../foo Relative path to the file foo in the directory above the current directory. windows On Microsoft Windows platforms, Tcl supports bothdrive-relative and UNC style names. Both / and \
may be used as directory separators in either typeof 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 atthe very least contain the server and share com-
ponents, 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: \\Host\share/file Absolute UNC path to a file called file in the root directory of the export point share on the host Host. Note that repeated use of file dirname on this path will give//Host/share, and will never give
just //Host.
c:foo Volume-relative path to a file foo
in the current directory on drive c. c:/foo Absolute path to a file foo in the Tcl Last change: 7.5 3Tcl Built-In Commands filename(1T)
root directory of drive c. foo\bar Relative path to a file bar in thefoo directory in the current direc-
tory on the current volume.\foo Volume-relative path to a file foo
in the root directory of the current volume.\\foo Volume-relative path to a file foo
in the root directory of the current volume. This is not a valid UNC path, so the assumption is that the extra backslashes are superfluous. TILDE SUBSTITUTION In addition to the file name rules described above, Tcl alsosupports 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 followedimmediately by a separator, then the $HOME environment vari-
able is substituted. Otherwise the characters between the tilde and the next separator are taken as a user name, whichis used to retrieve the user's home directory for substitu-
tion. The Macintosh and 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 otherwiseaccess the file. The behaviour of these paths when not try-
ing to interpret them is the same as on Unix. File namesthat have a tilde without a user name will be correctly sub-
stituted using the $HOME environment variable, just like for
Unix. PORTABILITY ISSUES 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. 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. Tcl Last change: 7.5 4Tcl Built-In Commands filename(1T)
On Windows platforms there are file and path length restric-
tions. 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 trailingdots '.' 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 nor-
malize'. Furthermore, a file name consisting only of dots '.........' or dots with trailing characters '.....abc' is illegal. KEYWORDS current directory, absolute file name, relative file name,volume-relative file name, portability
SEE ALSO
file(1T), glob(1T)ATTRIBUTES
See attributes(5) for descriptions of the following attri-
butes:_______________________________________
| ATTRIBUTE TYPE | ATTRIBUTE VALUE|
|____________________|__________________|_
| Availability | runtime/tcl-8 |
|____________________|__________________|_
| Interface Stability| Uncommitted ||____________________|_________________|
NOTES Source for Tcl is available on http://opensolaris.org. Tcl Last change: 7.5 5