198 lines
7.6 KiB
Plaintext
198 lines
7.6 KiB
Plaintext
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'\" Copyright (c) 1995-1996 Sun Microsystems, Inc.
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'\"
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'\" See the file "license.terms" for information on usage and redistribution
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'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
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'\"
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'\" SCCS: @(#) filename.n 1.7 96/04/11 17:03:14
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'\"
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.so man.macros
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.TH filename n 7.5 Tcl "Tcl Built-In Commands"
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.BS
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'\" Note: do not modify the .SH NAME line immediately below!
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.SH NAME
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filename \- File name conventions supported by Tcl commands
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.BE
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.SH INTRODUCTION
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.PP
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All Tcl commands and C procedures that take file names as arguments
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expect the file names to be in one of three forms, depending on the
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current platform. On each platform, Tcl supports file names in the
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standard forms(s) for that platform. In addition, on all platforms,
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Tcl supports a Unix-like syntax intended to provide a convenient way
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of constructing simple file names. However, scripts that are intended
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to be portable should not assume a particular form for file names.
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Instead, portable scripts must use the \fBfile split\fR and \fBfile
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join\fR commands to manipulate file names (see the \fBfile\fR manual
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entry for more details).
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.SH PATH TYPES
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.PP
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File names are grouped into three general types based on the starting point
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for the path used to specify the file: absolute, relative, and
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volume-relative. Absolute names are completely qualified, giving a path to
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the file relative to a particular volume and the root directory on that
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volume. Relative names are unqualified, giving a path to the file relative
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to the current working directory. Volume-relative names are partially
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qualified, either giving the path relative to the root directory on the
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current volume, or relative to the current directory of the specified
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volume. The \fBfile pathtype\fR command can be used to determine the
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type of a given path.
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.SH PATH SYNTAX
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.PP
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The rules for native names depend on the value reported in the Tcl
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array element \fBtcl_platform(platform)\fR:
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.TP 10
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\fBmac\fR
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On Apple Macintosh systems, Tcl supports two forms of path names. The
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normal Mac style names use colons as path separators. Paths may be
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relative or absolute, and file names may contain any character other
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than colon. A leading colon causes the rest of the path to be
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interpreted relative to the current directory. If a path contains a
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colon that is not at the beginning, then the path is interpreted as an
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absolute path. Sequences of two or more colons anywhere in the path
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are used to construct relative paths where \fB::\fR refers to the
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parent of the current directory, \fB:::\fR refers to the parent of the
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parent, and so forth.
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.RS
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.PP
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In addition to Macintosh style names, Tcl also supports a subset of
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Unix-like names. If a path contains no colons, then it is interpreted
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like a Unix path. Slash is used as the path separator. The file name
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\fB\&.\fR refers to the current directory, and \fB\&..\fR refers to the
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parent of the current directory. However, some names like \fB/\fR or
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\fB/..\fR have no mapping, and are interpreted as Macintosh names. In
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general, commands that generate file names will return Macintosh style
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names, but commands that accept file names will take both Macintosh
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and Unix-style names.
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.PP
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The following examples illustrate various forms of path names:
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.TP 15
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\fB:\fR
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Relative path to the current folder.
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.TP 15
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\fBMyFile\fR
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Relative path to a file named \fBMyFile\fR in the current folder.
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.TP 15
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\fBMyDisk:MyFile\fR
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Absolute path to a file named \fBMyFile\fR on the device named \fBMyDisk\fR.
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.TP 15
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\fB:MyDir:MyFile\fR
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Relative path to a file name \fBMyFile\fR in a folder named
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\fBMyDir\fR in the current folder.
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.TP 15
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\fB::MyFile\fR
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Relative path to a file named \fBMyFile\fR in the folder above the
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current folder.
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.TP 15
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\fB:::MyFile\fR
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Relative path to a file named \fBMyFile\fR in the folder two levels above the
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current folder.
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.TP 15
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\fB/MyDisk/MyFile\fR
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Absolute path to a file named \fBMyFile\fR on the device named
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\fBMyDisk\fR.
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.TP 15
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\fB\&../MyFile\fR
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Relative path to a file named \fBMyFile\fR in the folder above the
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current folder.
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.RE
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.TP
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\fBunix\fR
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On Unix platforms, Tcl uses path names where the components are
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separated by slashes. Path names may be relative or absolute, and
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file names may contain any character other than slash. The file names
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\fB\&.\fR and \fB\&..\fR are special and refer to the current directory
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and the parent of the current directory respectively. Multiple
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adjacent slash characters are interpreted as a single separator.
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The following examples illustrate various forms of path names:
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.RS
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.TP 15
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\fB/\fR
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Absolute path to the root directory.
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.TP 15
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\fB/etc/passwd\fR
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Absolute path to the file named \fBpasswd\fR in the directory
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\fBetc\fR in the root directory.
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.TP 15
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\fB\&.\fR
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Relative path to the current directory.
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.TP 15
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\fBfoo\fR
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Relative path to the file \fBfoo\fR in the current directory.
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.TP 15
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\fBfoo/bar\fR
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Relative path to the file \fBbar\fR in the directory \fBfoo\fR in the
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current directory.
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.TP 15
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\fB\&../foo\fR
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Relative path to the file \fBfoo\fR in the directory above the current
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directory.
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.RE
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.TP
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\fBwindows\fR
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On Microsoft Windows platforms, Tcl supports both drive-relative and UNC
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style names. Both \fB/\fR and \fB\e\fR may be used as directory separators
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in either type of name. Drive-relative names consist of an optional drive
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specifier followed by an absolute or relative path. UNC paths follow the
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general form \fB\e\eservername\esharename\epath\efile\fR. In both forms,
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the file names \fB.\fR and \fB..\fR are special and refer to the current
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directory and the parent of the current directory respectively. The
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following examples illustrate various forms of path names:
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.RS
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.TP 15
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\fB\&\e\eHost\eshare/file\fR
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Absolute UNC path to a file called \fBfile\fR in the root directory of
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the export point \fBshare\fR on the host \fBHost\fR.
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.TP 15
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\fBc:foo\fR
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Volume-relative path to a file \fBfoo\fR in the current directory on drive
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\fBc\fR.
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.TP 15
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\fBc:/foo\fR
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Absolute path to a file \fBfoo\fR in the root directory of drive
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\fBc\fR.
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.TP 15
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\fBfoo\ebar\fR
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Relative path to a file \fBbar\fR in the \fBfoo\fR directory in the current
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directory on the current volume.
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.TP 15
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\fB\&\efoo\fR
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Volume-relative path to a file \fBfoo\fR in the root directory of the current
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volume.
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.RE
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.SH TILDE SUBSTITUTION
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.PP
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In addition to the file name rules described above, Tcl also supports
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\fIcsh\fR-style tilde substitution. If a file name starts with a
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tilde, then the file name will be interpreted as if the first element
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is replaced with the location of the home directory for the given
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user. If the tilde is followed immediately by a separator, then the
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\fB$HOME\fR environment variable is substituted. Otherwise the
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characters between the tilde and the next separator are taken as a
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user name, which is used to retrieve the user's home directory for
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substitution.
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.PP
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The Macintosh and Windows platforms do not support tilde substitution
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when a user name follows the tilde. On these platforms, attempts to
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use a tilde followed by a user name will generate an error. File
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names that have a tilde without a user name will be substituted using
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the \fB$HOME\fR environment variable, just like for Unix.
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.SH PORTABILITY ISSUES
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.PP
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Not all file systems are case sensitive, so scripts should avoid code
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that depends on the case of characters in a file name. In addition,
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the character sets allowed on different devices may differ, so scripts
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should choose file names that do not contain special characters like:
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\fB<>:"/\e|\fR. The safest approach is to use names consisting of
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alphanumeric characters only. Also Windows 3.1 only supports file
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names with a root of no more than 8 characters and an extension of no
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more than 3 characters.
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.SH KEYWORDS
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current directory, absolute file name, relative file name,
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volume-relative file name, portability
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