1encoding(n) Tcl Built-In Commands encoding(n)
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8 encoding - Manipulate encodings
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11 encoding option ?arg arg ...?
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15 Strings in Tcl are logically a sequence of 16-bit Unicode characters.
16 These strings are represented in memory as a sequence of bytes that may
17 be in one of several encodings: modified UTF-8 (which uses 1 to 3 bytes
18 per character), 16-bit “Unicode” (which uses 2 bytes per character,
19 with an endianness that is dependent on the host architecture), and
20 binary (which uses a single byte per character but only handles a
21 restricted range of characters). Tcl does not guarantee to always use
22 the same encoding for the same string.
23 Different operating system interfaces or applications may generate
25 strings in other encodings such as Shift-JIS. The encoding command
26 helps to bridge the gap between Unicode and these other formats.
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29 Performs one of several encoding related operations, depending on
30 option. The legal options are:
31 encoding convertfrom ?encoding? data
33 Convert data to Unicode from the specified encoding. The char‐
34 acters in data are treated as binary data where the lower 8-bits
35 of each character is taken as a single byte. The resulting
36 sequence of bytes is treated as a string in the specified encod‐
37 ing. If encoding is not specified, the current system encoding
38 is used.
39 encoding convertto ?encoding? string
41 Convert string from Unicode to the specified encoding. The
42 result is a sequence of bytes that represents the converted
43 string. Each byte is stored in the lower 8-bits of a Unicode
44 character (indeed, the resulting string is a binary string as
45 far as Tcl is concerned, at least initially). If encoding is
46 not specified, the current system encoding is used.
47 encoding dirs ?directoryList?
49 Tcl can load encoding data files from the file system that
50 describe additional encodings for it to work with. This command
51 sets the search path for *.enc encoding data files to the list
52 of directories directoryList. If directoryList is omitted then
53 the command returns the current list of directories that make up
54 the search path. It is an error for directoryList to not be a
55 valid list. If, when a search for an encoding data file is hap‐
56 pening, an element in directoryList does not refer to a read‐
57 able, searchable directory, that element is ignored.
58 encoding names
60 Returns a list containing the names of all of the encodings that
61 are currently available. The encodings “utf-8” and “iso8859-1”
62 are guaranteed to be present in the list.
63 encoding system ?encoding?
65 Set the system encoding to encoding. If encoding is omitted then
66 the command returns the current system encoding. The system
67 encoding is used whenever Tcl passes strings to system calls.
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70 It is common practice to write script files using a text editor that
71 produces output in the euc-jp encoding, which represents the ASCII
72 characters as singe bytes and Japanese characters as two bytes. This
73 makes it easy to embed literal strings that correspond to non-ASCII
74 characters by simply typing the strings in place in the script. How‐
75 ever, because the source command always reads files using the current
76 system encoding, Tcl will only source such files correctly when the
77 encoding used to write the file is the same. This tends not to be true
78 in an internationalized setting. For example, if such a file was
79 sourced in North America (where the ISO8859-1 is normally used), each
80 byte in the file would be treated as a separate character that maps to
81 the 00 page in Unicode. The resulting Tcl strings will not contain the
82 expected Japanese characters. Instead, they will contain a sequence of
83 Latin-1 characters that correspond to the bytes of the original string.
84 The encoding command can be used to convert this string to the expected
85 Japanese Unicode characters. For example,
86 set s [encoding convertfrom euc-jp "\xA4\xCF"]
88 would return the Unicode string “\u306F”, which is the Hiragana letter
90 HA.
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93 Tcl_GetEncoding(3)
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96 encoding, unicode
97Tcl 8.1 encoding(n)