uuencode(1C) Communication Commands uuencode(1C)NAME
uuencode, uudecode - encode a binary file, or decode its encoded repre‐
sentation
SYNOPSIS
uuencode [source-file] decode_pathname
uuencode [-m] [source-file] decode_pathname
uudecode [-p] [encoded-file]
uudecode [-o outfile] [encoded-file]
DESCRIPTION
These commands encode and decode files as follows:
uuencode
The uuencode utility converts a binary file into an encoded representa‐
tion that can be sent using mail(1). It encodes the contents of source-
file, or the standard input if no source-file argument is given. The
decode_pathname argument is required. The decode_pathname is included
in the encoded file's header as the name of the file into which uude‐
code is to place the binary (decoded) data. uuencode also includes the
permission modes of source-file (except setuid, setgid, and sticky-
bits), so that decode_pathname is recreated with those same permission
modes.
uudecode
The uudecode utility reads an encoded-file, strips off any leading and
trailing lines added by mailer programs, and recreates the original
binary data with the filename and the mode specified in the header.
The encoded file is an ordinary portable character set text file; it
can be edited by any text editor. It is best only to change the mode or
decode_pathname in the header to avoid corrupting the decoded binary.
OPTIONS
The following options are supported:
uuencode
-m Encodes source-file using Base64 encoding and sends it
to standard output.
uudecode-o outfile Specifies a file pathname that should be used instead
of any pathname contained in the input data. Specifying
an outfile option-argument of /dev/stdout indicates
standard output.This allows uudecode to be used in a
pipeline.
-p Decodes encoded-file and sends it to standard output.
This allows uudecode to be used in a pipeline.
OPERANDS
The following operands are supported by uuencode and uudecode:
uuencode
decode_pathname The pathname of the file into which the uudecode util‐
ity will place the decoded file. If there are charac‐
ters in decode_pathname that are not in the portable
filename character set, the results are unspecified.
source-file A pathname of the file to be encoded.
uudecode
encoded-file The pathname of a file containing the output of uuen‐
code.
USAGE
See largefile(5) for the description of the behavior of uuencode and
uudecode when encountering files greater than or equal to 2 Gbyte ( 2
**31 bytes).
ENVIRONMENT VARIABLES
See environ(5) for descriptions of the following environment variables
that affect the execution of uuencode and uudecode: LANG, LC_ALL,
LC_CTYPE, LC_MESSAGES, and NLSPATH.
OUTPUT
stdout
uuencode Base64 Algorithm
The standard output is a text file, encoded in the character set of the
current locale, that begins with the line:
begin-base64 %s %s0 mode, decode_pathname
and ends with the line:
====
In both cases, the lines have no preceding or trailing blank charac‐
ters.
The encoding process represents 24-bit groups of input bits as output
strings of four encoded characters. Proceeding from left to right, a
24-bit input group is formed by concatenating three 8-bit input groups.
Each 24-bit input group is then treated as four concatenated 6-bit
groups, each of which is translated into a single digit in the Base64
alphabet. When encoding a bit stream by means of the Base64 encoding,
the bit stream is presumed to be ordered with the most-significant bit
first. That is, the first bit in the stream is the high-order bit in
the first byte, and the eighth bit is the low-order bit in the first
byte, and so on. Each 6-bit group is used as an index into an array of
64 printable characters, as shown in the following table.
Value Encoding Value Encoding Value Encoding Value Encoding
0 A 17 R 34 i 51 z
1 B 18 S 35 j 52 0
2 C 19 T 36 k 53 1
3 D 20 U 37 l 54 2
4 E 21 V 38 m 55 3
5 F 22 W 39 n 56 4
6 G 23 X 40 o 57 5
7 H 24 Y 41 p 58 6
8 I 25 Z 42 q 59 7
9 J 26 a 43 r 60 8
10 K 27 b 44 s 61 9
11 L 28 c 45 t 62 +
12 M 29 d 46 u 63 /
13 N 30 e 47 v
14 O 31 f 48 w (pad) =
15 P 32 g 49 x
16 Q 33 h 50 y
The character referenced by the index is placed in the output string.
The output stream (encoded bytes) is represented in lines of no more
than 76 characters each. All line breaks or other characters not found
in the table are ignored by decoding software (see uudecode).
Special processing is performed if fewer than 24 bits are available at
the end of a message or encapsulated part of a message. A full encoding
quantum is always completed at the end of a message. When fewer than 24
input bits are available in an input group, zero bits are added on the
right to form an integral number of 6-bit groups. Output character
positions that are not required to represent actual input data are set
to the equals (=) character. Since all Base64 input is an integral num‐
ber of octets, only the following cases can arise:
1. The final quantum of encoding input is an integral multiple of 24
bits. Here, the final unit of encoded output is an integral multi‐
ple of four characters with no '= ' padding.
2. The final quantum of encoding input is exactly 16 bits. Here, the
final unit of encoded output is three characters followed by one
'=' padding character.
3. The final quantum of encoding input is exactly 8 bits. Here, the
final unit of encoded output is two characters followed by two '='
padding characters.
A terminating "====" evaluates to nothing and denotes the end of the
encoded data.
uuencode Historical Algorithm
The standard output is a text file (encoded in the character set of the
current locale) that begins with the line:
begin %s %s\n, mode, decode_pathname
and ends with the line:
end\n
In both cases, the lines have no preceding or trailing blank charac‐
ters.
The algorithm that is used for lines between begin and end takes three
octets as input and writes four characters of output by splitting the
input at six-bit intervals into four octets, containing data in the
lower six bits only. These octets are converted to characters by adding
a value of 0x20 to each octet, so that each octet is in the range
0x20−0x5f, and each octet is assumed to represent a printable charac‐
ter. Each octect is then translated into the corresponding character
codes for the codeset in use in the current locale. For example, the
octet 0x41, representing 'A', would be translated to 'A' in the current
codeset, such as 0xc1 if the codeset were EBCDIC.
Where the bits of two octets are combined, the least significant bits
of the first octet are shifted left and combined with the most signifi‐
cant bits of the second octet shifted right. Thus, the three octets A,
B, C are converted into the four octets:
0x20 + (( A >> 2 ) & 0x3F)
0x20 + (((A << 4) ((B >> 4) & 0xF)) & 0x3F)
0x20 + (((B << 2) ((C >> 6) & 0x3)) & 0x3F)
0x20 + (( C ) & 0x3F)
These octets are then translated into the local character set.
Each encoded line contains a length character, equal to the number of
characters to be decoded plus 0x20 translated to the local character
set as described above, followed by the encoded characters. The maximum
number of octets to be encoded on each line is 45.
EXIT STATUS
The following exit values are returned:
0 Successful completion.
>0 An error occurred.
ATTRIBUTES
See attributes(5) for descriptions of the following attributes:
┌─────────────────────────────┬─────────────────────────────┐
│ ATTRIBUTE TYPE │ ATTRIBUTE VALUE │
├─────────────────────────────┼─────────────────────────────┤
│Availability │SUNWesu │
├─────────────────────────────┼─────────────────────────────┤
│Interface Stability │Standard │
└─────────────────────────────┴─────────────────────────────┘
SEE ALSOmail(1), mailx(1), uucp(1C), uux(1C), attributes(5), environ(5), large‐
file(5), standards(5)NOTES
The size of the encoded file is expanded by 35% (3 bytes become 4, plus
control information), causing it to take longer to transmit than the
equivalent binary.
The user on the remote system who is invoking uudecode (typically uucp)
must have write permission on the file specified in the decode_path‐
name.
If you invoke uuencode and then execute uudecode on a file in the same
directory, you will overwrite the original file.
SunOS 5.10 6 Aug 2003 uuencode(1C)
