NAME

       encoding - Manipulate encodings

SYNOPSIS

       encoding option ?arg arg ...?
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INTRODUCTION

       Strings  in  Tcl are logically a sequence of 16-bit Unicode characters.  These strings are represented in
       memory as a sequence of bytes that may be in one of several encodings: modified UTF-8 (which uses 1 to  3
       bytes  per  character),  16-bit  “Unicode”  (which uses 2 bytes per character, with an endianness that is
       dependent on the host architecture), and binary (which uses a single byte per character but only  handles
       a  restricted  range of characters).  Tcl does not guarantee to always use the same encoding for the same
       string.

       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
              (indeed,  the resulting string is a binary string as far as Tcl is concerned, at least initially).
              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.   The
              encodings “utf-8” and “iso8859-1” are guaranteed to be present in the list.

       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, unicode

Tcl                                                    8.1                                        encoding(3tcl)