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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24 File names are grouped into three general types based on the starting
25 point for the path used to specify the file: absolute, relative, and
26 volume-relative. Absolute names are completely qualified, giving a
27 path to the file relative to a particular volume and the root directory
28 on that volume. Relative names are unqualified, giving a path to the
29 file relative to the current working directory. Volume-relative names
30 are partially qualified, either giving the path relative to the root
31 directory on the current volume, or relative to the current directory
32 of the specified volume. The file pathtype command can be used to
33 determine the type of a given path.
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36 The rules for native names depend on the value reported in the Tcl
37 platform element of the tcl_platform array:
38 Unix On Unix and Apple MacOS X platforms, Tcl uses path names
40 where the components are separated by slashes. Path names
41 may be relative or absolute, and file names may contain any
42 character other than slash. The file names . and .. are spe‐
43 cial and refer to the current directory and the parent of the
44 current directory respectively. Multiple adjacent slash
45 characters are interpreted as a single separator. Any number
46 of trailing slash characters at the end of a path are simply
47 ignored, so the paths foo, foo/ and foo// are all identical,
48 and in particular foo/ does not necessarily mean a directory
49 is being referred.
50 The following examples illustrate various forms of path
52 names:
53 / Absolute path to the root directory.
55 /etc/passwd Absolute path to the file named passwd in the
57 directory etc in the root directory.
58 . Relative path to the current directory.
60 foo Relative path to the file foo in the current
62 directory.
63 foo/bar Relative path to the file bar in the directory
65 foo in the current directory.
66 ../foo Relative path to the file foo in the directory
68 above the current directory.
69 Windows On Microsoft Windows platforms, Tcl supports both drive-rela‐
71 tive and UNC style names. Both / and \ may be used as direc‐
72 tory separators in either type of name. Drive-relative names
73 consist of an optional drive specifier followed by an abso‐
74 lute or relative path. UNC paths follow the general form
75 \\servername\sharename\path\file, but must at the very least
76 contain the server and share components, i.e. \\server‐
77 name\sharename. In both forms, the file names . and .. are
78 special and refer to the current directory and the parent of
79 the current directory respectively. The following examples
80 illustrate various forms of path names:
81 \\Host\share/file
83 Absolute UNC path to a file called file in the
84 root directory of the export point share on
85 the host Host. Note that repeated use of file
86 dirname on this path will give //Host/share,
87 and will never give just //Host.
88 c:foo Volume-relative path to a file foo in the cur‐
90 rent directory on drive c.
91 c:/foo Absolute path to a file foo in the root direc‐
93 tory of drive c.
94 foo\bar Relative path to a file bar in the foo direc‐
96 tory in the current directory on the current
97 volume.
98 \foo Volume-relative path to a file foo in the root
100 directory of the current volume.
101 \\foo Volume-relative path to a file foo in the root
103 directory of the current volume. This is not
104 a valid UNC path, so the assumption is that
105 the extra backslashes are superfluous.
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108 In addition to the file name rules described above, Tcl also supports
109 csh-style tilde substitution. If a file name starts with a tilde, then
110 the file name will be interpreted as if the first element is replaced
111 with the location of the home directory for the given user. If the
112 tilde is followed immediately by a separator, then the $HOME environ‐
113 ment variable is substituted. Otherwise the characters between the
114 tilde and the next separator are taken as a user name, which is used to
115 retrieve the user's home directory for substitution. This works on
116 Unix, MacOS X and Windows (except very old releases).
117 Old Windows platforms do not support tilde substitution when a user
119 name follows the tilde. On these platforms, attempts to use a tilde
120 followed by a user name will generate an error that the user does not
121 exist when Tcl attempts to interpret that part of the path or otherwise
122 access the file. The behaviour of these paths when not trying to
123 interpret them is the same as on Unix. File names that have a tilde
124 without a user name will be correctly substituted using the $HOME envi‐
125 ronment variable, just like for Unix.
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128 Not all file systems are case sensitive, so scripts should avoid code
129 that depends on the case of characters in a file name. In addition,
130 the character sets allowed on different devices may differ, so scripts
131 should choose file names that do not contain special characters like:
132 <>:?"/\|. The safest approach is to use names consisting of alphanu‐
133 meric characters only. Care should be taken with filenames which con‐
134 tain spaces (common on Windows systems) and filenames where the back‐
135 slash is the directory separator (Windows native path names). Also
136 Windows 3.1 only supports file names with a root of no more than 8
137 characters and an extension of no more than 3 characters.
138 On Windows platforms there are file and path length restrictions. Com‐
140 plete paths or filenames longer than about 260 characters will lead to
141 errors in most file operations.
142 Another Windows peculiarity is that any number of trailing dots “.” in
144 filenames are totally ignored, so, for example, attempts to create a
145 file or directory with a name “foo.” will result in the creation of a
146 file/directory with name “foo”. This fact is reflected in the results
147 of file normalize. Furthermore, a file name consisting only of dots
148 “.........” or dots with trailing characters “.....abc” is illegal.
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151 file(n), glob(n)
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154 current directory, absolute file name, relative file name, volume-rela‐
155 tive file name, portability
156Tcl 7.5 filename(n)