1UUENCODE(1P) POSIX Programmer's Manual UUENCODE(1P)
2
6 This manual page is part of the POSIX Programmer's Manual. The Linux
7 implementation of this interface may differ (consult the corresponding
8 Linux manual page for details of Linux behavior), or the interface may
9 not be implemented on Linux.
10
12 uuencode - encode a binary file
13
15 uuencode [-m][file] decode_pathname
16
18 The uuencode utility shall write an encoded version of the named input
19 file, or standard input if no file is specified, to standard output.
20 The output shall be encoded using one of the algorithms described in
21 the STDOUT section and shall include the file access permission bits
22 (in chmod octal or symbolic notation) of the input file and the
23 decode_pathname, for re-creation of the file on another system that
24 conforms to this volume of IEEE Std 1003.1-2001.
25
27 The uuencode utility shall conform to the Base Definitions volume of
28 IEEE Std 1003.1-2001, Section 12.2, Utility Syntax Guidelines.
29 The following option shall be supported by the implementation:
31 -m Encode the output using the MIME Base64 algorithm described in
33 STDOUT. If -m is not specified, the historical algorithm
34 described in STDOUT shall be used.
35
38 The following operands shall be supported:
39 decode_pathname
41 The pathname of the file into which the uudecode utility shall
43 place the decoded file. Specifying a decode_pathname operand of
44 /dev/stdout shall indicate that uudecode is to use standard out‐
45 put. If there are characters in decode_pathname that are not in
46 the portable filename character set the results are unspecified.
47 file A pathname of the file to be encoded.
49
52 See the INPUT FILES section.
53
55 Input files can be files of any type.
56
58 The following environment variables shall affect the execution of uuen‐
59 code:
60 LANG Provide a default value for the internationalization variables
62 that are unset or null. (See the Base Definitions volume of
63 IEEE Std 1003.1-2001, Section 8.2, Internationalization Vari‐
64 ables for the precedence of internationalization variables used
65 to determine the values of locale categories.)
66 LC_ALL If set to a non-empty string value, override the values of all
68 the other internationalization variables.
69 LC_CTYPE
71 Determine the locale for the interpretation of sequences of
72 bytes of text data as characters (for example, single-byte as
73 opposed to multi-byte characters in arguments and input files).
74 LC_MESSAGES
76 Determine the locale that should be used to affect the format
77 and contents of diagnostic messages written to standard error.
78 NLSPATH
80 Determine the location of message catalogs for the processing of
81 LC_MESSAGES .
82
85 Default.
86
88 uuencode Base64 Algorithm
89 The standard output shall be a text file (encoded in the character set
90 of the current locale) that begins with the line:
91 "begin-base64 %s %s\n", <mode>, <decode_pathname>
94 and ends with the line:
96 "====\n"
99 In both cases, the lines shall have no preceding or trailing <blank>s.
101 The encoding process represents 24-bit groups of input bits as output
103 strings of four encoded characters. Proceeding from left to right, a
104 24-bit input group shall be formed by concatenating three 8-bit input
105 groups. Each 24-bit input group then shall be treated as four concate‐
106 nated 6-bit groups, each of which shall be translated into a single
107 digit in the Base64 alphabet. When encoding a bit stream via the Base64
108 encoding, the bit stream shall be presumed to be ordered with the most-
109 significant bit first. That is, the first bit in the stream shall be
110 the high-order bit in the first byte, and the eighth bit shall be the
111 low-order bit in the first byte, and so on. Each 6-bit group is used as
112 an index into an array of 64 printable characters, as shown in uuencode
113 Base64 Values .
114 Table: uuencode Base64 Values
116 Value Encoding Value Encoding Value Encoding Value Encoding
118 0 A 17 R 34 i 51 z
119 1 B 18 S 35 j 52 0
120 2 C 19 T 36 k 53 1
121 3 D 20 U 37 l 54 2
122 4 E 21 V 38 m 55 3
123 5 F 22 W 39 n 56 4
124 6 G 23 X 40 o 57 5
125 7 H 24 Y 41 p 58 6
126 8 I 25 Z 42 q 59 7
127 9 J 26 a 43 r 60 8
128 10 K 27 b 44 s 61 9
129 11 L 28 c 45 t 62 +
130 12 M 29 d 46 u 63 /
131 13 N 30 e 47 v
132 14 O 31 f 48 w (pad)──────────
134 15 P 32 g 49 x
135 16 Q 33 h 50 y
136 The character referenced by the index shall be placed in the output
138 string.
139 The output stream (encoded bytes) shall be represented in lines of no
141 more than 76 characters each. All line breaks or other characters not
142 found in the table shall be ignored by decoding software (see uudecode
143 ).
144 Special processing shall be performed if fewer than 24 bits are avail‐
146 able at the end of a message or encapsulated part of a message. A full
147 encoding quantum shall always be completed at the end of a message.
148 When fewer than 24 input bits are available in an input group, zero
149 bits shall be added (on the right) to form an integral number of 6-bit
150 groups. Output character positions that are not required to represent
151 actual input data shall be set to the character '=' . Since all Base64
152 input is an integral number of octets, only the following cases can
153 arise:
154 1. The final quantum of encoding input is an integral multiple of 24
156 bits; here, the final unit of encoded output shall be an integral
157 multiple of 4 characters with no '=' padding.
158 2. The final quantum of encoding input is exactly 16 bits; here, the
160 final unit of encoded output shall be three characters followed by
161 one '=' padding character.
162 3. The final quantum of encoding input is exactly 8 bits; here, the
164 final unit of encoded output shall be two characters followed by
165 two '=' padding characters.
166 A terminating "====" evaluates to nothing and denotes the end of the
168 encoded data.
169 uuencode Historical Algorithm
171 The standard output shall be a text file (encoded in the character set
172 of the current locale) that begins with the line:
173 "begin %s %s\n" <mode>, <decode_pathname>
176 and ends with the line:
178 "end\n"
181 In both cases, the lines shall have no preceding or trailing <blank>s.
183 The algorithm that shall be used for lines in between begin and end
185 takes three octets as input and writes four characters of output by
186 splitting the input at six-bit intervals into four octets, containing
187 data in the lower six bits only. These octets shall be converted to
188 characters by adding a value of 0x20 to each octet, so that each octet
189 is in the range [0x20,0x5f], and then it shall be assumed to represent
190 a printable character in the ISO/IEC 646:1991 standard encoded charac‐
191 ter set. It then shall be translated into the corresponding character
192 codes for the codeset in use in the current locale. (For example, the
193 octet 0x41, representing 'A', would be translated to 'A' in the current
194 codeset, such as 0xc1 if it were EBCDIC.)
195 Where the bits of two octets are combined, the least significant bits
197 of the first octet shall be shifted left and combined with the most
198 significant bits of the second octet shifted right. Thus the three
199 octets A, B, C shall be converted into the four octets:
200 0x20 + (( A >> 2 ) & 0x3F)
203 0x20 + (((A << 4) | ((B >> 4) & 0xF)) & 0x3F)
204 0x20 + (((B << 2) | ((C >> 6) & 0x3)) & 0x3F)
205 0x20 + (( C ) & 0x3F)
206 These octets then shall be translated into the local character set.
208 Each encoded line contains a length character, equal to the number of
210 characters to be decoded plus 0x20 translated to the local character
211 set as described above, followed by the encoded characters. The maxi‐
212 mum number of octets to be encoded on each line shall be 45.
213
215 The standard error shall be used only for diagnostic messages.
216
218 None.
219
221 None.
222
224 The following exit values shall be returned:
225 0 Successful completion.
227 >0 An error occurred.
229
232 Default.
233 The following sections are informative.
235
237 The file is expanded by 35 percent (each three octets become four, plus
238 control information) causing it to take longer to transmit.
239 Since this utility is intended to create files to be used for data
241 interchange between systems with possibly different codesets, and to
242 represent binary data as a text file, the ISO/IEC 646:1991 standard was
243 chosen for a midpoint in the algorithm as a known reference point. The
244 output from uuencode is a text file on the local system. If the output
245 were in the ISO/IEC 646:1991 standard codeset, it might not be a text
246 file (at least because the <newline>s might not match), and the goal of
247 creating a text file would be defeated. If this text file was then car‐
248 ried to another machine with the same codeset, it would be perfectly
249 compatible with that system's uudecode. If it was transmitted over a
250 mail system or sent to a machine with a different codeset, it is
251 assumed that, as for every other text file, some translation mechanism
252 would convert it (by the time it reached a user on the other system)
253 into an appropriate codeset. This translation only makes sense from the
254 local codeset, not if the file has been put into a ISO/IEC 646:1991
255 standard representation first. Similarly, files processed by uuencode
256 can be placed in pax archives, intermixed with other text files in the
257 same codeset.
258
260 None.
261
263 A new algorithm was added at the request of the international community
264 to parallel work in RFC 2045 (MIME). As with the historical uuencode
265 format, the Base64 Content-Transfer-Encoding is designed to represent
266 arbitrary sequences of octets in a form that is not humanly readable. A
267 65-character subset of the ISO/IEC 646:1991 standard is used, enabling
268 6 bits to be represented per printable character. (The extra 65th char‐
269 acter, '=', is used to signify a special processing function.)
270 This subset has the important property that it is represented identi‐
272 cally in all versions of the ISO/IEC 646:1991 standard, including US
273 ASCII, and all characters in the subset are also represented identi‐
274 cally in all versions of EBCDIC. The historical uuencode algorithm does
275 not share this property, which is the reason that a second algorithm
276 was added to the ISO POSIX-2 standard.
277 The string "====" was used for the termination instead of the end used
279 in the original format because the latter is a string that could be
280 valid encoded input.
281 In an early draft, the -m option was named -b (for Base64), but it was
283 renamed to reflect its relationship to the RFC 2045. A -u was also
284 present to invoke the default algorithm, but since this was not histor‐
285 ical practice, it was omitted as being unnecessary.
286 See the RATIONALE section in uudecode for the derivation of the
288 /dev/stdout symbol.
289
291 None.
292
294 chmod(), mailx, uudecode
295
297 Portions of this text are reprinted and reproduced in electronic form
298 from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
299 -- Portable Operating System Interface (POSIX), The Open Group Base
300 Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
301 Electrical and Electronics Engineers, Inc and The Open Group. In the
302 event of any discrepancy between this version and the original IEEE and
303 The Open Group Standard, the original IEEE and The Open Group Standard
304 is the referee document. The original Standard can be obtained online
305 at http://www.opengroup.org/unix/online.html .
306IEEE/The Open Group 2003 UUENCODE(1P)