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There are many variations of the above rules which must be
taken into account in a decoder program. Here are the most
frequent:
- Many old encoders do not pay attention to the special rule of
encoding the 0 value, and encode it into a space character instead of
the ```'' character. This is not an ``error,'' but rather a
potential problem when mailing or posting the file.
- Some encoders add a 62nd character to each encoded line:
sometimes a character looping from ``a'' to ``z'' over and over
again. This technique could be used to detect missing lines, but
confuses some decoders.
- If the length of the input file is not a multiple of three, some
encoders omit the ``unnecessary'' characters at the end of the last
data line.
- Sometimes, the ``empty'' data line at the end is omitted, and at
other times, the line is just completely empty (without the
```'').
There is also some confusion how to properly terminate a line. Most
encoders simply use the convention of the local system (DOS encoders
using CRLF, Unix encoders using LF, Mac encoders using CR), but with
respect to the MIME standard, the encoding library uses CRLF on all
systems. This causes a slight problem with some Unix decoders, which
look for ``end'' followed directly by LF (as four characters in
total). Such programs report ``end not found'', but nevertheless
decode the file correctly.
Next: Example
Up: Uuencoding
Previous: Splitting Files
m68k build daemon
2002-04-15