encoding(3tcl)
NAME
encoding - Manipulate encodings
SYNOPSIS
encoding option ?arg arg ...? ______________________________________________________________________________
INTRODUCTION
Strings in Tcl are encoded using 16-bit Unicode characters. Different operating system interfaces or applications may generate strings in other encodings such as Shift-JIS. The encoding command helps to bridge the gap between Unicode and these other formats.
DESCRIPTION
Performs one of several encoding related operations, depending on
option. The legal options are:
encoding convertfrom ?encoding? data
Convert data to Unicode from the specified encoding. The
characters in data are treated as binary data where the lower
8-bits of each character is taken as a single byte. The
resulting sequence of bytes is treated as a string in the
specified encoding. If encoding is not specified, the current
system encoding is used.
encoding convertto ?encoding? string
Convert string from Unicode to the specified encoding. The
result is a sequence of bytes that represents the converted
string. Each byte is stored in the lower 8-bits of a Unicode
character. If encoding is not specified, the current system
encoding is used.
encoding dirs ?directoryList?
Tcl can load encoding data files from the file system that
describe additional encodings for it to work with. This command
sets the search path for *.enc encoding data files to the list
of directories directoryList. If directoryList is omitted then
the command returns the current list of directories that make up
the search path. It is an error for directoryList to not be a
valid list. If, when a search for an encoding data file is
happening, an element in directoryList does not refer to a
readable, searchable directory, that element is ignored.
encoding names
Returns a list containing the names of all of the encodings that
are currently available.
encoding system ?encoding?
Set the system encoding to encoding. If encoding is omitted then
the command returns the current system encoding. The system
encoding is used whenever Tcl passes strings to system calls.
EXAMPLE
It is common practice to write script files using a text editor that
produces output in the euc-jp encoding, which represents the ASCII
characters as singe bytes and Japanese characters as two bytes. This
makes it easy to embed literal strings that correspond to non-ASCII
characters by simply typing the strings in place in the script.
However, because the source command always reads files using the
current system encoding, Tcl will only source such files correctly when
the encoding used to write the file is the same. This tends not to be
true in an internationalized setting. For example, if such a file was
sourced in North America (where the ISO8859-1 is normally used), each
byte in the file would be treated as a separate character that maps to
the 00 page in Unicode. The resulting Tcl strings will not contain the
expected Japanese characters. Instead, they will contain a sequence of
Latin-1 characters that correspond to the bytes of the original string.
The encoding command can be used to convert this string to the expected
Japanese Unicode characters. For example,
set s [encoding convertfrom euc-jp "\xA4\xCF"]
would return the Unicode string "\u306F", which is the Hiragana letter
HA.
SEE ALSO
Tcl_GetEncoding(3tcl)
KEYWORDS
encoding
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