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UTF8 (5) | File formats and conventions | Unix Manual Pages | :man

NAME

utf8 - "UTF-8, a transformation format of ISO 10646"

CONTENTS

Synopsis
Description
See Also
Standards

SYNOPSIS

ENCODING "UTF-8"

DESCRIPTION

The UTF-8 encoding represents UCS-4 characters as a sequence of octets, using between 1 and 6 for each character. It is backwards compatible with ASCII, so 0x00-0x7f refer to the ASCII character set. The multibyte encoding of non- ASCII characters consist entirely of bytes whose high order bit is set. The actual encoding is represented by the following table:
[0x00000000 - 0x0000007f] [00000000.0bbbbbbb] -> 0bbbbbbb
[0x00000080 - 0x000007ff] [00000bbb.bbbbbbbb] -> 110bbbbb, 10bbbbbb
[0x00000800 - 0x0000ffff] [bbbbbbbb.bbbbbbbb] ->
1110bbbb, 10bbbbbb, 10bbbbbb
[0x00010000 - 0x001fffff] [00000000.000bbbbb.bbbbbbbb.bbbbbbbb] ->
11110bbb, 10bbbbbb, 10bbbbbb, 10bbbbbb
[0x00200000 - 0x03ffffff] [000000bb.bbbbbbbb.bbbbbbbb.bbbbbbbb] ->
111110bb, 10bbbbbb, 10bbbbbb, 10bbbbbb, 10bbbbbb
[0x04000000 - 0x7fffffff] [0bbbbbbb.bbbbbbbb.bbbbbbbb.bbbbbbbb] ->
1111110b, 10bbbbbb, 10bbbbbb, 10bbbbbb, 10bbbbbb, 10bbbbbb

If more than a single representation of a value exists (for example, 0x00; 0xC0 0x80; 0xE0 0x80 0x80) the shortest representation is always used. Longer ones are detected as an error as they pose a potential security risk, and destroy the 1:1 character:octet sequence mapping.

SEE ALSO

euc(5)
.Rs "Hello World"
.Re
.Rs "UTF-8, a transformation format of ISO 10646"
.Re
.Rs "The Unicode Standard, Version 3.0"
.Re

STANDARDS


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