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Updated: Wednesday, February 9, 2022

encoding (1t)


encoding - Manipulate encodings


encoding option ?arg arg ...?


encoding(1t)                 Tcl Built-In Commands                encoding(1t)


       encoding - Manipulate encodings

       encoding option ?arg arg ...?

       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.

       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 char-
              acters 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 encod-
              ing.   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 hap-
              pening, an element in directoryList does not refer  to  a  read-
              able, 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.

       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.  How-
       ever, 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

       See attributes(7) for descriptions of the following attributes:

       |Availability   | runtime/tcl-8    |
       |Stability      | Uncommitted      |


       encoding, unicode

       Source  code  for open source software components in Oracle Solaris can
       be found at https://www.oracle.com/downloads/opensource/solaris-source-

       This     software     was    built    from    source    available    at
       https://github.com/oracle/solaris-userland.   The  original   community
       source was downloaded from  http://prdownloads.sourceforge.net/tcl/tcl-

       Further information about this software can be found on the open source
       community website at https://www.tcl.tk/.

Tcl                                   8.1                         encoding(1t)