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1989-04-24
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BTOA(1) USER COMMANDS BTOA(1)
NAME
btoa - encode/decode binary to printable ASCII
SYNOPSIS
btoa -adhor input filename output filename
DESCRIPTION
Btoa is a filter which reads binary bytes from the input
file and generates printable ASCII characters on the output
file. It attaches a header and a checksum to the archive. It
can also reverse this, creating a binary file from the
archive.
Since last version of btoa/atob, several new features have
been added. The most obvious one is that atob has been
integrated with btoa. They are now the same program which is
called with different arguments. Another is the ability to
repair damaged archives.
The new version is compatible with the old version, that is,
it can still encode and decode old btoa files.
Btoa has an option to decode the archive, restoring the
binary bytes. It strips the input file until it finds a
valid header, and continues decoding until the end mark is
found. It recognices both old- and new-style headers, and
can decode both. It is possible to leave out the destination
name when decoding new-style archives, because the name is
stored in the header. Entering a name will override the
autonaming function.
It is possible to leave out the file names and redirect
stdin and stdout with '<' and '>' to the desired files. This
is to maintain compatibility with earlier versions of btoa.
Btoa now adds a single byte checksum to each row in the
archive. When an error is found, diagnosis automatically
starts and produces a diagnosis file which can be used to
extract the damaged part from an errorfree archive. The
extracted part can then be used to correct the damaged
archive. Btoa has options to perform the reparation
automatically. This is especially useful when downloading
data converted to text files, and occasionally finding that
an archive file of considerable size turns is corrupted.
FEATURES
Btoa encodes 4 binary bytes into 5 characters, expanding the
file by 25%. As a special case 4 zeroes will be encoded as
'z' and 4 spaces as 'y'. This makes it possible to compress
the archive a bit.
Last change: 21 February 1989 1
BTOA(1) USER COMMANDS BTOA(1)
OPTIONS
-h Shows help on btoa.
-a Switches to atob (decoding) mode.
-o Switches to old version of btoa.
-d Extracts repair file from diagnosis file. This assumes
that an undamaged version of the archive and a file
called
-r Repairs the damaged archive. A file named 'btoa.rep'
must be present for this to work.
EXAMPLES
Below follows a description of a normal repair session.
Lines beginning with 'Local>' were typed on the computer to
which the file was downloaded. Accordingly, lines typed on
the connected computer will begin with 'Remote>'. Sending a
file to the other computer will be noted as 'transmit file'.
A normal repairing procedure is as follows: Local> btoa -a
file.btoa btoa: Bad checksum on line 2648. btoa: Starting
diagnosis. btoa: Diagnosis output to 'btoa.dia'. Local>
transmit btoa.dia
Remote> btoa -d file.btoa btoa: Repair output to 'btoa.rep'.
Remote> transmit btoa.rep
Local> btoa -a btoa.rep btoa: Repaired archive written to
'btoa.rdy'.
You can now erase file.btoa and decode btoa.rdy using 'btoa
-a btoa.rdy'.
AUTHORS
Paul Rutter Joe Orost Stefan Parmark
KNOWN BUGS
Btoa will not work properly unless the input is a true file
or a redirected one. This is because file positions are col-
lected during diagnosis for later reference when producing
the diagnosis file. The bug is actually in fseek() which
only can reposition 'real' files.
Send bug reports to d84sp@efd.lth.se (Stefan Parmark).
Last change: 21 February 1989 2