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254 bytes in length. When transferring archives via
modem using the XMODEM protocol, files are transferred
in 128 byte blocks. If the file is not an integer
multiple of 128 bytes in length, as the majority of
files are not, XMODEM "pads" the file with blanks or
nulls. Consequently, an extra disk sector gets added to
the end of an archive! It is easy to fix this problem
by using a disk doctor program. Simply change the link
for the second last sector in the archive to (0,255).
You should have no problem extracting files from
XMODEM downloaded archives, because ARC will ignore
this XMODEM padding. BEFORE YOU APPEND to an archive,
you should fix this problem, or else the files appended
to the archive will not be able to be de-archived.
We have added a new command to ARC to check an
archive for this type of problem. Simply type:
arc/f archname[.arc]
ARC will trace the track,sector links for the
archive and get rid of the last sector in the archive.
If the archive is ok and the link for the last sector
is already (0,255) as it should be, then ARC does
nothing and prints the message:
archive is ok.
ARC VERSION 2.20 PAGE - 22
If the archive is bad and the link is anything other
than (0,255) then ARC will go to the second last sector
in the archive and change its link to (0,255). This
drops the extra sector added by the XMODEM padding. ARC
won't free up the deleted sector, nor will it adjust
the directory block count for the archive. If you need
the extra block free, then validate the disk to get it
back.
ARC VERSION 2.20 PAGE - 23
Extracting Files from an Archive.
arc/x[d] <[d:]archfile[.arc]> [pattern1] [pattern2] ...
This command is used to extract files from an
archive. If no patterns are specified, then ARC will
extract all files from the archive. When patterns are
given, then only those files in the archive which match
one of the patterns will be extracted.
Since ARC no longer supports encryption of data
files, it won't be able to handle an encrypted file.
You will have to use a previous version of ARC. The
file will de-archive ok but it will still be encrypted.
This is the only exception to the rule that ARC will
handle any archive created by any previous version of
ARC. Just for the sake of completeness, however, we
will write a little external utility which can be used
to un-encrypt the file once de-archived and include it
with later versions of ARC.
Some examples:
arc/x a:sq
Extracts all files from "sq.arc" on drive 8,0 and
puts them on the default directory.
arc/x a:sq *
Same as the above
arc/xf b:temp.arc
Extracts all files from "temp.arc" on drive 8,1 and
puts them on the diskette in drive f: (10,1)
arc/e c:book030386 chapter1
Extracts only the file 'chapter1' from the archive
'book030386' on drive c:
NOTE: arc/x and arc/e are synonyms