1filename(n) Tcl Built-In Commands filename(n)
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8 filename - File name conventions supported by Tcl commands
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12 All Tcl commands and C procedures that take file names as arguments
13 expect the file names to be in one of three forms, depending on the
14 current platform. On each platform, Tcl supports file names in the
15 standard forms(s) for that platform. In addition, on all platforms,
16 Tcl supports a Unix-like syntax intended to provide a convenient way of
17 constructing simple file names. However, scripts that are intended to
18 be portable should not assume a particular form for file names.
19 Instead, portable scripts must use the file split and file join com‐
20 mands to manipulate file names (see the file manual entry for more
21 details).
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25 File names are grouped into three general types based on the starting
26 point for the path used to specify the file: absolute, relative, and
27 volume-relative. Absolute names are completely qualified, giving a
28 path to the file relative to a particular volume and the root directory
29 on that volume. Relative names are unqualified, giving a path to the
30 file relative to the current working directory. Volume-relative names
31 are partially qualified, either giving the path relative to the root
32 directory on the current volume, or relative to the current directory
33 of the specified volume. The file pathtype command can be used to
34 determine the type of a given path.
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38 The rules for native names depend on the value reported in the Tcl
39 array element tcl_platform(platform):
40 mac On Apple Macintosh systems, Tcl supports two forms of path
42 names. The normal Mac style names use colons as path separa‐
43 tors. Paths may be relative or absolute, and file names may
44 contain any character other than colon. A leading colon
45 causes the rest of the path to be interpreted relative to the
46 current directory. If a path contains a colon that is not at
47 the beginning, then the path is interpreted as an absolute
48 path. Sequences of two or more colons anywhere in the path
49 are used to construct relative paths where :: refers to the
50 parent of the current directory, ::: refers to the parent of
51 the parent, and so forth.
52 In addition to Macintosh style names, Tcl also supports a
54 subset of Unix-like names. If a path contains no colons,
55 then it is interpreted like a Unix path. Slash is used as
56 the path separator. The file name . refers to the current
57 directory, and .. refers to the parent of the current direc‐
58 tory. However, some names like / or /.. have no mapping, and
59 are interpreted as Macintosh names. In general, commands
60 that generate file names will return Macintosh style names,
61 but commands that accept file names will take both Macintosh
62 and Unix-style names.
63 The following examples illustrate various forms of path
65 names:
66 : Relative path to the current folder.
68 MyFile Relative path to a file named MyFile in the
70 current folder.
71 MyDisk:MyFile Absolute path to a file named MyFile on the
73 device named MyDisk.
74 :MyDir:MyFile Relative path to a file name MyFile in a
76 folder named MyDir in the current folder.
77 ::MyFile Relative path to a file named MyFile in the
79 folder above the current folder.
80 :::MyFile Relative path to a file named MyFile in the
82 folder two levels above the current folder.
83 /MyDisk/MyFile Absolute path to a file named MyFile on the
85 device named MyDisk.
86 ../MyFile Relative path to a file named MyFile in the
88 folder above the current folder.
89 unix On Unix platforms, Tcl uses path names where the components
91 are separated by slashes. Path names may be relative or
92 absolute, and file names may contain any character other than
93 slash. The file names . and .. are special and refer to the
94 current directory and the parent of the current directory
95 respectively. Multiple adjacent slash characters are inter‐
96 preted as a single separator. The following examples illus‐
97 trate various forms of path names:
98 / Absolute path to the root directory.
100 /etc/passwd Absolute path to the file named passwd in the
102 directory etc in the root directory.
103 . Relative path to the current directory.
105 foo Relative path to the file foo in the current
107 directory.
108 foo/bar Relative path to the file bar in the directory
110 foo in the current directory.
111 ../foo Relative path to the file foo in the directory
113 above the current directory.
114 windows On Microsoft Windows platforms, Tcl supports both drive-rela‐
116 tive and UNC style names. Both / and \ may be used as direc‐
117 tory separators in either type of name. Drive-relative names
118 consist of an optional drive specifier followed by an abso‐
119 lute or relative path. UNC paths follow the general form
120 \\servername\sharename\path\file, but must at the very least
121 contain the server and share components, i.e. \\server‐
122 name\sharename. In both forms, the file names . and .. are
123 special and refer to the current directory and the parent of
124 the current directory respectively. The following examples
125 illustrate various forms of path names:
126 \\Host\share/file
128 Absolute UNC path to a file called file in the
129 root directory of the export point share on
130 the host Host. Note that repeated use of file
131 dirname on this path will give //Host/share,
132 and will never give just /fB//Host/fR.
133 c:foo Volume-relative path to a file foo in the cur‐
135 rent directory on drive c.
136 c:/foo Absolute path to a file foo in the root direc‐
138 tory of drive c.
139 foo\bar Relative path to a file bar in the foo direc‐
141 tory in the current directory on the current
142 volume.
143 \foo Volume-relative path to a file foo in the root
145 directory of the current volume.
146 \\foo Volume-relative path to a file foo in the root
148 directory of the current volume. This is not
149 a valid UNC path, so the assumption is that
150 the extra backslashes are superfluous.
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154 In addition to the file name rules described above, Tcl also supports
155 csh-style tilde substitution. If a file name starts with a tilde, then
156 the file name will be interpreted as if the first element is replaced
157 with the location of the home directory for the given user. If the
158 tilde is followed immediately by a separator, then the $HOME environ‐
159 ment variable is substituted. Otherwise the characters between the
160 tilde and the next separator are taken as a user name, which is used to
161 retrieve the user's home directory for substitution.
162 The Macintosh and Windows platforms do not support tilde substitution
164 when a user name follows the tilde. On these platforms, attempts to
165 use a tilde followed by a user name will generate an error that the
166 user does not exist when Tcl attempts to interpret that part of the
167 path or otherwise access the file. The behaviour of these paths when
168 not trying to interpret them is the same as on Unix. File names that
169 have a tilde without a user name will be correctly substituted using
170 the $HOME environment variable, just like for Unix.
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174 Not all file systems are case sensitive, so scripts should avoid code
175 that depends on the case of characters in a file name. In addition,
176 the character sets allowed on different devices may differ, so scripts
177 should choose file names that do not contain special characters like:
178 <>:"/\|. The safest approach is to use names consisting of alphanu‐
179 meric characters only. Also Windows 3.1 only supports file names with
180 a root of no more than 8 characters and an extension of no more than 3
181 characters.
182 On Windows platforms there are file and path length restrictions. Com‐
184 plete paths or filenames longer than about 260 characters will lead to
185 errors in most file operations.
186 Another Windows peculiarity is that any number of trailing dots '.' in
188 filenames are totally ignored, so, for example, attempts to create a
189 file or directory with a name "foo." will result in the creation of a
190 file/directory with name "foo". This fact is reflected in the results
191 of 'file normalize'. Furthermore, a file name consisting only of dots
192 '.........' or dots with trailing characters '.....abc' is illegal.
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195 current directory, absolute file name, relative file name, volume-rela‐
196 tive file name, portability
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200 file(n), glob(n)
201Tcl 7.5 filename(n)