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7 .TH UUENCODE 1C "Aug 6, 2003"
8 .SH NAME
9 uuencode, uudecode \- encode a binary file, or decode its encoded
10 representation
11 .SH SYNOPSIS
12 .LP
13 .nf
14 \fBuuencode\fR [\fIsource-file\fR] \fIdecode_pathname\fR
15 .fi
17 .LP
18 .nf
19 \fBuuencode\fR [\fB-m\fR] [\fIsource-file\fR] \fIdecode_pathname\fR
20 .fi
22 .LP
23 .nf
24 \fBuudecode\fR [\fB-p\fR] [\fIencoded-file\fR]
25 .fi
27 .LP
28 .nf
29 \fBuudecode\fR [\fB-o\fR \fIoutfile\fR] [\fIencoded-file\fR]
30 .fi
32 .SH DESCRIPTION
33 .sp
34 .LP
35 These commands encode and decode files as follows:
36 .SS "uuencode"
37 .sp
38 .LP
39 The \fBuuencode\fR utility converts a binary file into an encoded
40 representation that can be sent using \fBmail\fR(1). It encodes the contents of
41 \fIsource-file\fR, or the standard input if no \fIsource-file\fR argument is
42 given. The \fIdecode_pathname\fR argument is required. The
43 \fIdecode_pathname\fR is included in the encoded file's header as the name of
44 the file into which \fBuudecode\fR is to place the binary (decoded) data.
45 \fBuuencode\fR also includes the permission modes of \fIsource-file\fR (except
46 \fBsetuid\fR, \fBsetgid\fR, and sticky-bits), so that \fIdecode_pathname\fR is
47 recreated with those same permission modes.
48 .SS "uudecode"
49 .sp
50 .LP
51 The \fBuudecode\fR utility reads an \fIencoded-file\fR, strips off any leading
52 and trailing lines added by mailer programs, and recreates the original binary
53 data with the filename and the mode specified in the header.
54 .sp
55 .LP
56 The encoded file is an ordinary portable character set text file; it can be
57 edited by any text editor. It is best only to change the mode or
58 \fIdecode_pathname\fR in the header to avoid corrupting the decoded binary.
59 .SH OPTIONS
60 .sp
61 .LP
62 The following options are supported:
63 .SS "uuencode"
64 .sp
65 .ne 2
66 .na
67 \fB\fB-m\fR\fR
68 .ad
69 .RS 6n
70 Encodes \fIsource-file\fR using Base64 encoding and sends it to standard
71 output.
72 .RE
74 .SS "uudecode"
75 .sp
76 .ne 2
77 .na
78 \fB\fB-o\fR \fIoutfile\fR\fR
79 .ad
80 .RS 14n
81 Specifies a file pathname that should be used instead of any pathname contained
82 in the input data. Specifying an \fIoutfile\fR option-argument of
83 \fB/dev/stdout\fR indicates standard output.This allows \fBuudecode\fR to be
84 used in a pipeline.
85 .RE
87 .sp
88 .ne 2
89 .na
90 \fB\fB-p\fR\fR
91 .ad
92 .RS 14n
93 Decodes \fIencoded-file\fR and sends it to standard output. This allows
94 \fBuudecode\fR to be used in a pipeline.
95 .RE
97 .SH OPERANDS
98 .sp
99 .LP
100 The following operands are supported by \fBuuencode\fR and \fBuudecode\fR:
101 .SS "uuencode"
102 .sp
103 .ne 2
104 .na
105 \fB\fIdecode_pathname\fR\fR
106 .ad
107 .RS 19n
108 The pathname of the file into which the \fBuudecode\fR utility will place the
109 decoded file. If there are characters in \fIdecode_pathname\fR that are not in
110 the portable filename character set, the results are unspecified.
111 .RE
113 .sp
114 .ne 2
115 .na
116 \fB\fIsource-file\fR\fR
117 .ad
118 .RS 19n
119 A pathname of the file to be encoded.
120 .RE
122 .SS "uudecode"
123 .sp
124 .ne 2
125 .na
126 \fB\fIencoded-file\fR\fR
127 .ad
128 .RS 16n
129 The pathname of a file containing the output of \fBuuencode\fR.
130 .RE
132 .SH USAGE
133 .sp
134 .LP
135 See \fBlargefile\fR(5) for the description of the behavior of \fBuuencode\fR
136 and \fBuudecode\fR when encountering files greater than or equal to 2 Gbyte (
137 2^31 bytes).
138 .SH ENVIRONMENT VARIABLES
139 .sp
140 .LP
141 See \fBenviron\fR(5) for descriptions of the following environment variables
142 that affect the execution of \fBuuencode\fR and \fBuudecode\fR: \fBLANG\fR,
143 \fBLC_ALL\fR, \fBLC_CTYPE\fR, \fBLC_MESSAGES\fR, and \fBNLSPATH\fR.
144 .SH OUTPUT
145 .sp
146 .LP
147 stdout
148 .SS "uuencode Base64 Algorithm"
149 .sp
150 .LP
151 The standard output is a text file, encoded in the character set of the current
152 locale, that begins with the line:
153 .sp
154 .in +2
155 .nf
156 begin-base64 %s %s\n, \fImode\fR, \fIdecode_pathname\fR
157 .fi
158 .in -2
159 .sp
161 .sp
162 .LP
163 and ends with the line:
164 .sp
165 .in +2
166 .nf
167 ====
168 .fi
169 .in -2
170 .sp
172 .sp
173 .LP
174 In both cases, the lines have no preceding or trailing blank characters.
175 .sp
176 .LP
177 The encoding process represents 24-bit groups of input bits as output strings
178 of four encoded characters. Proceeding from left to right, a 24-bit input
179 group is formed by concatenating three 8-bit input groups. Each 24-bit input
180 group is then treated as four concatenated 6-bit groups, each of which is
181 translated into a single digit in the Base64 alphabet. When encoding a bit
182 stream by means of the Base64 encoding, the bit stream is presumed to be
183 ordered with the most-significant bit first. That is, the first bit in the
184 stream is the high-order bit in the first byte, and the eighth bit is the
185 low-order bit in the first byte, and so on. Each 6-bit group is used as an
186 index into an array of 64 printable characters, as shown in the following
187 table.
188 .sp
189 .in +2
190 .nf
191 Value Encoding Value Encoding Value Encoding Value Encoding
192 0 A 17 R 34 i 51 z
193 1 B 18 S 35 j 52 0
194 2 C 19 T 36 k 53 1
195 3 D 20 U 37 l 54 2
196 4 E 21 V 38 m 55 3
197 5 F 22 W 39 n 56 4
198 6 G 23 X 40 o 57 5
199 7 H 24 Y 41 p 58 6
200 8 I 25 Z 42 q 59 7
201 9 J 26 a 43 r 60 8
202 10 K 27 b 44 s 61 9
203 11 L 28 c 45 t 62 +
204 12 M 29 d 46 u 63 /
205 13 N 30 e 47 v
206 14 O 31 f 48 w (pad) =
207 15 P 32 g 49 x
208 16 Q 33 h 50 y
209 .fi
210 .in -2
211 .sp
213 .sp
214 .LP
215 The character referenced by the index is placed in the output string.
216 .sp
217 .LP
218 The output stream (encoded bytes) is represented in lines of no more than 76
219 characters each. All line breaks or other characters not found in the table are
220 ignored by decoding software (see \fBuudecode\fR).
221 .sp
222 .LP
223 Special processing is performed if fewer than 24 bits are available at the end
224 of a message or encapsulated part of a message. A full encoding quantum is
225 always completed at the end of a message. When fewer than 24 input bits are
226 available in an input group, zero bits are added on the right to form an
227 integral number of 6-bit groups. Output character positions that are not
228 required to represent actual input data are set to the equals (\fB=\fR)
229 character. Since all Base64 input is an integral number of octets, only the
230 following cases can arise:
231 .RS +4
232 .TP
233 1.
234 The final quantum of encoding input is an integral multiple of 24 bits.
235 Here, the final unit of encoded output is an integral multiple of four
236 characters with no '\fB=\fR ' padding.
237 .RE
238 .RS +4
239 .TP
240 2.
241 The final quantum of encoding input is exactly 16 bits. Here, the final unit
242 of encoded output is three characters followed by one '\fB=\fR' padding
243 character.
244 .RE
245 .RS +4
246 .TP
247 3.
248 The final quantum of encoding input is exactly 8 bits. Here, the final unit
249 of encoded output is two characters followed by two '\fB=\fR' padding
250 characters.
251 .RE
252 .sp
253 .LP
254 A terminating "\fB====\fR" evaluates to nothing and denotes the end of the
255 encoded data.
256 .SS "uuencode Historical Algorithm"
257 .sp
258 .LP
259 The standard output is a text file (encoded in the character set of the current
260 locale) that begins with the line:
261 .sp
262 .in +2
263 .nf
264 begin %s %s\en, \fImode\fR, \fIdecode_pathname\fR
265 .fi
266 .in -2
267 .sp
269 .sp
270 .LP
271 and ends with the line:
272 .sp
273 .in +2
274 .nf
275 end\en
276 .fi
277 .in -2
278 .sp
280 .sp
281 .LP
282 In both cases, the lines have no preceding or trailing blank characters.
283 .sp
284 .LP
285 The algorithm that is used for lines between \fBbegin\fR and \fBend\fR takes
286 three octets as input and writes four characters of output by splitting the
287 input at six-bit intervals into four octets, containing data in the lower six
288 bits only. These octets are converted to characters by adding a value of
289 \fB0x20\fR to each octet, so that each octet is in the range
290 \fB0x20\(mi0x5f\fR, and each octet is assumed to represent a printable
291 character. Each octect is then translated into the corresponding character
292 codes for the codeset in use in the current locale. For example, the octet
293 \fB0x41\fR, representing '\fBA\fR', would be translated to '\fBA\fR' in the
294 current codeset, such as \fB0xc1\fR if the codeset were \fBEBCDIC\fR.
295 .sp
296 .LP
297 Where the bits of two octets are combined, the least significant bits of the
298 first octet are shifted left and combined with the most significant bits of the
299 second octet shifted right. Thus, the three octets \fBA\fR, \fBB\fR, \fBC\fR
300 are converted into the four octets:
301 .sp
302 .in +2
303 .nf
304 0x20 + (( A >> 2 ) & 0x3F)
305 0x20 + (((A << 4) ((B >> 4) & 0xF)) & 0x3F)
306 0x20 + (((B << 2) ((C >> 6) & 0x3)) & 0x3F)
307 0x20 + (( C ) & 0x3F)
308 .fi
309 .in -2
310 .sp
312 .sp
313 .LP
314 These octets are then translated into the local character set.
315 .sp
316 .LP
317 Each encoded line contains a length character, equal to the number of
318 characters to be decoded plus \fB0x20\fR translated to the local character set
319 as described above, followed by the encoded characters. The maximum number of
320 octets to be encoded on each line is 45.
321 .SH EXIT STATUS
322 .sp
323 .LP
324 The following exit values are returned:
325 .sp
326 .ne 2
327 .na
328 \fB\fB0\fR\fR
329 .ad
330 .RS 6n
331 Successful completion.
332 .RE
334 .sp
335 .ne 2
336 .na
337 \fB\fB>0\fR\fR
338 .ad
339 .RS 6n
340 An error occurred.
341 .RE
343 .SH ATTRIBUTES
344 .sp
345 .LP
346 See \fBattributes\fR(5) for descriptions of the following attributes:
347 .sp
349 .sp
350 .TS
351 box;
352 c | c
353 l | l .
354 ATTRIBUTE TYPE ATTRIBUTE VALUE
355 _
356 Interface Stability Standard
357 .TE
359 .SH SEE ALSO
360 .sp
361 .LP
362 \fBmail\fR(1), \fBmailx\fR(1), \fBuucp\fR(1C), \fBuux\fR(1C),
363 \fBattributes\fR(5), \fBenviron\fR(5), \fBlargefile\fR(5), \fBstandards\fR(5)
364 .SH NOTES
365 .sp
366 .LP
367 The size of the encoded file is expanded by 35% (3 bytes become 4, plus control
368 information), causing it to take longer to transmit than the equivalent binary.
369 .sp
370 .LP
371 The user on the remote system who is invoking \fBuudecode\fR (typically
372 \fBuucp\fR) must have write permission on the file specified in the
373 \fIdecode_pathname\fR.
374 .sp
375 .LP
376 If you invoke \fBuuencode\fR and then execute \fBuudecode\fR on a file in the
377 same directory, you will overwrite the original file.