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