= Uuencoding =

'''Uuencoding''' refers to the use of the '''`uuencode(1)`''' and '''`uudecode(1)`''' utilities for transfer of binary files between Unix hosts.

<<TableOfContents>>

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== Structure ==

A uuencoded file looks like:

{{{
begin 644 cat.txt
#0V%T
`
end
}}}

The `begin` line includes the file permissions and name.

Each line is a chunk of binary data represented by printable characters. Each character represents 6 bits of the original binary data. The chunks contain up to 45 bytes of original data or 60 bytes of encoded data. Each line is prefixed by a character representing the original size of that chunk. The most common prefixes are `M`, which represents a full chunk, and {{{`}}}, which represents an empty line.

The `end` line always follows one such empty line.

The above file is the result of uuencoding "Cat".

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== Code Points ==

Every 6 bits are encoded as a printable character by adding 32 to the binary value. The exception is a null value.

||'''Binary Value'''||'''Encoded Value'''||'''ASCII Code Point'''||
||00||96||```||
||01||33||`!`||
||02||34||`"`||
||03||35||`#`||
||04||36||`$`||
||05||37||`%`||
||06||38||`&`||
||07||39||`'`||
||08||40||`(`||
||09||41||`)`||
||10||42||`*`||
||11||43||`+`||
||12||44||`,`||
||13||45||`-`||
||14||46||`.`||
||15||47||`/`||
||16||48||`0`||
||17||49||`1`||
||18||50||`2`||
||19||51||`3`||
||20||52||`4`||
||21||53||`5`||
||22||54||`6`||
||23||55||`7`||
||24||56||`8`||
||25||57||`9`||
||26||58||`:`||
||27||59||`;`||
||28||60||`<`||
||29||61||`=`||
||30||62||`>`||
||31||63||`?`||
||32||64||`@`||
||33||65||`A`||
||34||66||`B`||
||35||67||`C`||
||36||68||`D`||
||37||69||`E`||
||38||70||`F`||
||39||71||`G`||
||40||72||`H`||
||41||73||`I`||
||42||74||`J`||
||43||75||`K`||
||44||76||`L`||
||45||77||`M`||
||46||78||`N`||
||47||79||`O`||
||48||80||`P`||
||49||81||`Q`||
||50||82||`R`||
||51||83||`S`||
||52||84||`T`||
||53||85||`U`||
||54||86||`V`||
||55||87||`W`||
||56||88||`X`||
||57||89||`Y`||
||58||90||`Z`||
||59||91||`[`||
||60||92||`\`||
||61||93||`]`||
||62||94||`^`||
||63||95||`_`||

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== History ==

Uuencoding was developed in response to poor handling of different character encodings and character sets across [[Email/MTA|message transfer agents]]. In particular, this addressed the need to send files between Unix systems.

The names and designs of the `uuencode(1)` and `uudecode(1)` utilities comes from the [[Protocols/UUCP|Unix-to-Unix Copy protocol]] (UUCP).



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CategoryRicottone