# man > UUENCODE(5)

[_UUENCODE_(5)](https://www.chedong.com/phpMan.php/man/UUENCODE/5/markdown)                              File Formats Manual                             [_UUENCODE_(5)](https://www.chedong.com/phpMan.php/man/UUENCODE/5/markdown)

## NAME
       uuencode - format of an encoded uuencode file

## DESCRIPTION
       Files output by [uuencode(1)](https://www.chedong.com/phpMan.php/man/uuencode/1/markdown) consist of a header line, followed by a number of body lines, and
       a  trailer  line.  The [uudecode(1)](https://www.chedong.com/phpMan.php/man/uudecode/1/markdown) command will ignore any lines preceding the header or fol‐
       lowing the trailer.  Lines preceding a header must not, of course, look like a header.

       The header line is distinguished by having the first 5 characters  be  _begin_  followed  by  a
       space,  or else a hyphen and either _base64_ or _encoded_ or both (also separated with a hyphen).
       The _base64_ option says the file has been encoded using base64.  The _encoded_ option  says  the
       output  file  _name_ has been base64 encoded.  It is never encoded with traditional uuencoding.
       This is a GNU extension.  These are followed by a mode (in octal), and a string  which  names
       the  remote  file.  The mode is separated from the _begin_ clause and the file name by a single
       space character.

### Traditional uuencoding
       The traditional _uuencoded_ file body consists of a number of lines, each at most 62 characters
       long (including the trailing newline). These consist of a character count letter, followed by
       the encoded characters, followed by a newline.  The character  count  is  a  single  printing
       character,  and  represents  an integer, the number of bytes the rest of the line represents.
       Such integers are always in the range from 0 to 63 and can be determined by  subtracting  the
       character space (octal 40) from the character.

       Groups  of  3  bytes  are  stored in 4 characters, 6 bits per character.  All are offset by a
       space to make the characters printing.  The last line may  be  shorter  than  the  normal  45
       bytes.   If  the size is not a multiple of 3, this fact can be determined by the value of the
       count on the last line.  Extra garbage will be included to make the character count a  multi‐
       ple  of 4.  The body is terminated by a line with a count of zero.  This line consists of one
       ASCII space.

       The trailer line consists of _end_ on a line by itself.

### base64 encoding
       _base64_ encoded files follow the specified format for the body,  but  also  include  a  _begin-_
       _base64_ header and a trailer line of four _=_ characters.

## EXAMPLES
            begin-base64-encoded 644 VE9ETw==
       This  introduces a base64 encoded file named, _TODO_ with that name encoded using base64 encod‐
       ing.

            begin-encoded 644 5$]$3P``
       This introduces an encoded file named, _TODO_ with that name encoded using uuencoding.  The en‐
       coding is a lot less friendly.  Please prefer base64 encoding.

## CONFORMING TO
       IEEE Std 1003.1, plus extensions

       The _-encoded_ suffix to the _begin_ header line is a GNU extension.  Recipients  must  have  the
       GNU _uudecode_ program to decode them.

## SEE ALSO
       [uuencode(1)](https://www.chedong.com/phpMan.php/man/uuencode/1/markdown), [uudecode(1)](https://www.chedong.com/phpMan.php/man/uudecode/1/markdown), [base64(1GNU)](https://www.chedong.com/phpMan.php/man/base64/1GNU/markdown)

## HISTORY
       The _uuencode_ file format appeared in BSD 4.0 .

                                                                                         [_UUENCODE_(5)](https://www.chedong.com/phpMan.php/man/UUENCODE/5/markdown)