Man Pages

uuencode(1p) - phpMan uuencode(1p) - phpMan

Command: man perldoc info search(apropos)  

UUENCODE(1P)               POSIX Programmer's Manual              UUENCODE(1P)

       This manual page is part of the POSIX Programmer's Manual.  The Linux implementation of this interface may dif-
       fer (consult the corresponding Linux manual page for details of Linux behavior), or the interface  may  not  be
       implemented on Linux.

       uuencode - encode a binary file

       uuencode [-m][file] decode_pathname

       The  uuencode  utility  shall write an encoded version of the named input file, or standard input if no file is
       specified, to standard output. The output shall be encoded using one of the algorithms described in the  STDOUT
       section  and  shall  include the file access permission bits (in chmod octal or symbolic notation) of the input
       file and the decode_pathname, for re-creation of the file on another system that conforms  to  this  volume  of
       IEEE Std 1003.1-2001.

       The  uuencode utility shall conform to the Base Definitions volume of IEEE Std 1003.1-2001, Section 12.2, Util-
       ity Syntax Guidelines.

       The following option shall be supported by the implementation:

       -m     Encode the output using the MIME Base64 algorithm described in STDOUT.  If -m is not specified, the his-
              torical algorithm described in STDOUT shall be used.

       The following operands shall be supported:


              The  pathname  of  the  file  into which the uudecode utility shall place the decoded file. Specifying a
              decode_pathname operand of /dev/stdout shall indicate that uudecode is to use standard output. If  there
              are  characters  in  decode_pathname that are not in the portable filename character set the results are

       file   A pathname of the file to be encoded.

       See the INPUT FILES section.

       Input files can be files of any type.

       The following environment variables shall affect the execution of uuencode:

       LANG   Provide a default value for the internationalization variables that are unset or  null.  (See  the  Base
              Definitions  volume  of IEEE Std 1003.1-2001, Section 8.2, Internationalization Variables for the prece-
              dence of internationalization variables used to determine the values of locale categories.)

       LC_ALL If set to a non-empty string value, override the values of all the other internationalization variables.

              Determine  the locale for the interpretation of sequences of bytes of text data as characters (for exam-
              ple, single-byte as opposed to multi-byte characters in arguments and input files).

              Determine the locale that should be used to affect the format and contents of diagnostic messages  writ-
              ten to standard error.

              Determine the location of message catalogs for the processing of LC_MESSAGES .


   uuencode Base64 Algorithm
       The  standard output shall be a text file (encoded in the character set of the current locale) that begins with
       the line:

              "begin-base64 %s %s\n", <mode>, <decode_pathname>

       and ends with the line:


       In both cases, the lines shall have no preceding or trailing <blank>s.

       The encoding process represents 24-bit groups of input bits as output strings of four encoded characters.  Pro-
       ceeding  from  left  to  right, a 24-bit input group shall be formed by concatenating three 8-bit input groups.
       Each 24-bit input group then shall be treated as four concatenated 6-bit groups, each of which shall be  trans-
       lated  into  a single digit in the Base64 alphabet. When encoding a bit stream via the Base64 encoding, the bit
       stream shall be presumed to be ordered with the most-significant bit first.  That is,  the  first  bit  in  the
       stream  shall  be  the  high-order  bit in the first byte, and the eighth bit shall be 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 uuencode Base64 Values .

                                                Table: uuencode Base64 Values

                              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 shall be placed in the output string.

       The  output  stream  (encoded bytes) shall be represented in lines of no more than 76 characters each. All line
       breaks or other characters not found in the table shall be ignored by decoding software (see uudecode ).

       Special processing shall be performed if fewer than 24 bits are available at the end of a message  or  encapsu-
       lated  part of a message. A full encoding quantum shall always be completed at the end of a message. When fewer
       than 24 input bits are available in an input group, zero bits shall be 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 shall
       be set to the character '=' . Since all Base64 input is an integral number 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 shall be an integral multiple of 4 characters with no '=' padding.

        2. The final quantum of encoding input is exactly 16 bits; here, the final unit of  encoded  output  shall  be
           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 shall be 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 shall be 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:


       In both cases, the lines shall have no preceding or trailing <blank>s.

       The algorithm that shall be used for lines in 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 shall be converted to characters by adding a value of 0x20 to each octet, so that
       each octet is in the range [0x20,0x5f], and then it shall be assumed to represent a printable character in  the
       ISO/IEC 646:1991  standard  encoded character set. It then shall be 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 it were EBCDIC.)

       Where  the bits of two octets are combined, the least significant bits of the first octet shall be shifted left
       and combined with the most significant bits of the second octet shifted right. Thus the three octets  A,  B,  C
       shall be 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 then shall be translated into the local character set.

       Each encoded line contains a length character, equal to the number of characters to be decoded plus 0x20 trans-
       lated to the local character set as described above, followed by the encoded characters.  The maximum number of
       octets to be encoded on each line shall be 45.

       The standard error shall be used only for diagnostic messages.



       The following exit values shall be returned:

        0     Successful completion.

       >0     An error occurred.


       The following sections are informative.

       The file is expanded by 35 percent (each three octets become four, plus control information) causing it to take
       longer to transmit.

       Since this utility is intended to create files to be used for data interchange between  systems  with  possibly
       different codesets, and to represent binary data as a text file, the ISO/IEC 646:1991 standard was chosen for a
       midpoint in the algorithm as a known reference point. The output from uuencode is a text file on the local sys-
       tem. If the output were in the ISO/IEC 646:1991 standard codeset, it might not be a text file (at least because
       the <newline>s might not match), and the goal of creating a text file would be defeated. If this text file  was
       then  carried  to  another  machine  with the same codeset, it would be perfectly compatible with that system's
       uudecode. If it was transmitted over a mail system or sent to a machine with a different codeset, it is assumed
       that,  as for every other text file, some translation mechanism would convert it (by the time it reached a user
       on the other system) into an appropriate codeset. This translation only makes sense from the local codeset, not
       if  the  file has been put into a ISO/IEC 646:1991 standard representation first. Similarly, files processed by
       uuencode can be placed in pax archives, intermixed with other text files in the same codeset.


       A new algorithm was added at the request of the international community to parallel work in RFC 2045 (MIME). As
       with  the  historical  uuencode format, the Base64 Content-Transfer-Encoding is designed to represent arbitrary
       sequences of octets in a form that is not humanly readable. A 65-character subset of the ISO/IEC 646:1991 stan-
       dard  is  used,  enabling  6 bits to be represented per printable character. (The extra 65th character, '=', is
       used to signify a special processing function.)

       This  subset  has  the  important  property  that  it  is  represented  identically  in  all  versions  of  the
       ISO/IEC 646:1991  standard,  including  US ASCII, and all characters in the subset are also represented identi-
       cally in all versions of EBCDIC. The historical uuencode algorithm does not share this property, which  is  the
       reason that a second algorithm was added to the ISO POSIX-2 standard.

       The  string "====" was used for the termination instead of the end used in the original format because the lat-
       ter is a string that could be valid encoded input.

       In an early draft, the -m option was named -b (for Base64), but it was renamed to reflect its  relationship  to
       the  RFC 2045.  A  -u was also present to invoke the default algorithm, but since this was not historical prac-
       tice, it was omitted as being unnecessary.

       See the RATIONALE section in uudecode for the derivation of the /dev/stdout symbol.


       chmod(), mailx, uudecode

       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Stan-
       dard  for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifica-
       tions Issue 6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics Engineers,  Inc  and  The
       Open Group. In the event of any discrepancy between this version and the original IEEE and The Open Group Stan-
       dard, the original IEEE and The Open Group Standard is the referee  document.  The  original  Standard  can  be
       obtained online at .

IEEE/The Open Group                  2003                         UUENCODE(1P)