Editing Uuencoding (section)

== Encoded format ==
A uuencoded file starts with a header line of the form:
 begin <mode> <file><newline>
<code><mode></code> is the file's [[File permissions#Numeric notation|Unix file permissions]] as three octal digits (e.g. 644, 744). This is typically only significant to [[Unix-like]] operating systems.

<code><file></code> is the file name to be used when recreating the binary data.

<code><newline></code> signifies a [[newline]] character, used to terminate each line.

Each data line uses the format:
 <length character><formatted characters><newline>

<code><length character></code> is a character indicating the number of data bytes which have been encoded on that line. This is an [[ASCII]] character determined by adding 32 to the actual byte count, with the sole exception of a grave accent "`" (ASCII code 96) signifying zero bytes. All data lines, except the last (if the data length was not divisible by 45), have 45 bytes of encoded data (60 characters after encoding). Therefore, the vast majority of length values are 'M', (32 + 45 = ASCII code 77 or "M").

<code><formatted characters></code> are encoded characters.  See {{section link||Formatting mechanism}} for more details on the actual implementation.

The file ends with two lines:
 `<newline>
 end<newline>

The second to last line is also a character indicating the line length, with the grave accent signifying zero bytes.

As a complete file, the uuencoded output for a plain text file named cat.txt containing only the characters ''Cat'' would be
 begin 644 cat.txt
 #0V%T
 `
 end

The begin line is a standard uuencode header; the '#' indicates that its line encodes three characters; the last two lines appear at the end of all uuencoded files.