Subversion Repositories or1k

'\"

'\" Copyright (c) 1995-1996 Sun Microsystems, Inc.

'\"

'\" See the file "license.terms" for information on usage and redistribution

'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.

'\"

'\" RCS: @(#) $Id: filename.n,v 1.1.1.1 2002-01-16 10:25:24 markom Exp $

'\"

.so man.macros

.TH filename n 7.5 Tcl "Tcl Built-In Commands"

.BS

'\" Note:  do not modify the .SH NAME line immediately below!

.SH NAME

filename \- File name conventions supported by Tcl commands

.BE

.SH INTRODUCTION

.PP

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, Tcl supports file names in the

standard forms(s) for that platform.  In addition, on all platforms,

Tcl supports a Unix-like syntax intended to provide a convenient way

of constructing 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 \fBfile split\fR and \fBfile

join\fR commands to manipulate file names (see the \fBfile\fR manual

entry for more details).

.SH PATH TYPES

.PP

File names are grouped into three general types based on the starting point

for the path used to specify the file: absolute, 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 file relative

to the current working directory.  Volume-relative names are partially

qualified, either giving the path relative to the root directory on the

current volume, or relative to the current directory of the specified

volume.  The \fBfile pathtype\fR command can be used to determine the

type of a given path.

.SH PATH SYNTAX

.PP

The rules for native names depend on the value reported in the Tcl

array element \fBtcl_platform(platform)\fR:

.TP 10

\fBmac\fR

On Apple Macintosh systems, 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 character 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 \fB::\fR refers to the

parent of the current directory, \fB:::\fR refers to the parent of the

parent, and so forth.

.RS

.PP

In addition to Macintosh style names, Tcl also supports 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

\fB\&.\fR refers to the current directory, and \fB\&..\fR refers to the

parent of the current directory.  However, some names like \fB/\fR or

\fB/..\fR 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

and Unix-style names.

.PP

The following examples illustrate various forms of path names:

.TP 15

\fB:\fR

Relative path to the current folder.

.TP 15

\fBMyFile\fR

Relative path to a file named \fBMyFile\fR in the current folder.

.TP 15

\fBMyDisk:MyFile\fR

Absolute path to a file named \fBMyFile\fR on the device named \fBMyDisk\fR.

.TP 15

\fB:MyDir:MyFile\fR

Relative path to a file name \fBMyFile\fR in a folder named

\fBMyDir\fR in the current folder.

.TP 15

\fB::MyFile\fR

Relative path to a file named \fBMyFile\fR in the folder above the

current folder.

.TP 15

\fB:::MyFile\fR

Relative path to a file named \fBMyFile\fR in the folder two levels above the

current folder.

.TP 15

\fB/MyDisk/MyFile\fR

Absolute path to a file named \fBMyFile\fR on the device named

\fBMyDisk\fR.

.TP 15

\fB\&../MyFile\fR

Relative path to a file named \fBMyFile\fR in the folder above the

current folder.

.RE

.TP

\fBunix\fR

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

\fB\&.\fR and \fB\&..\fR 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.

The following examples illustrate various forms of path names:

.RS

.TP 15

\fB/\fR

Absolute path to the root directory.

.TP 15

\fB/etc/passwd\fR

Absolute path to the file named \fBpasswd\fR in the directory

\fBetc\fR in the root directory.

.TP 15

\fB\&.\fR

Relative path to the current directory.

.TP 15

\fBfoo\fR

Relative path to the file \fBfoo\fR in the current directory.

.TP 15

\fBfoo/bar\fR

Relative path to the file \fBbar\fR in the directory \fBfoo\fR in the

current directory.

.TP 15

\fB\&../foo\fR

Relative path to the file \fBfoo\fR in the directory above the current

directory.

.RE

.TP

\fBwindows\fR

On Microsoft Windows platforms, Tcl supports both drive-relative and UNC

style names.  Both \fB/\fR and \fB\e\fR 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 \fB\e\eservername\esharename\epath\efile\fR.  In both forms,

the file names \fB.\fR and \fB..\fR 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:

.RS

.TP 15

\fB\&\e\eHost\eshare/file\fR

Absolute UNC path to a file called \fBfile\fR in the root directory of

the export point \fBshare\fR on the host \fBHost\fR.

.TP 15

\fBc:foo\fR

Volume-relative path to a file \fBfoo\fR in the current directory on drive

\fBc\fR.

.TP 15

\fBc:/foo\fR

Absolute path to a file \fBfoo\fR in the root directory of drive

\fBc\fR.

.TP 15

\fBfoo\ebar\fR

Relative path to a file \fBbar\fR in the \fBfoo\fR directory in the current

directory on the current volume.

.TP 15

\fB\&\efoo\fR

Volume-relative path to a file \fBfoo\fR in the root directory of the current

volume.

.RE

.SH TILDE SUBSTITUTION

.PP

In addition to the file name rules described above, Tcl also supports

\fIcsh\fR-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

\fB$HOME\fR 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 user's home directory for

substitution.

.PP

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.  File

names that have a tilde without a user name will be substituted using

the \fB$HOME\fR environment variable, just like for Unix.

.SH PORTABILITY ISSUES

.PP

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:

\fB<>:"/\e|\fR.  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.

.SH KEYWORDS

current directory, absolute file name, relative file name,

volume-relative file name, portability