shar
<tool, file format> ("Shell archive", after ar and tar) Any of the many
Unix programs that creates a flattened representation of one or more files, with
the unique property that it can be unflattened (the original files extracted)
merely by feeding it through a standard Unix shell. The output of shar, known as
a "shar file" or "sharchive", can be distributed to anyone running Unix, and no
special unpacking software is required.
Sharchives are intriguing in that they are typically created by shell scripts;
the script that produces sharchives is thus a script which produces
self-unpacking scripts, which may themselves contain scripts. The disadvantage
of sharchives are that they are an ideal venue for Trojan horse attacks and
that, for recipients not running Unix, no simple un-sharchiving program is
possible; sharchives can and do make use of arbitrarily-powerful shell features
and other Unix commands.
Different implementations of shar vary in sophistication. Some just uuencode
each input file and output commands to uudecode the result, others include
extensive checking to make sure the files have been transferred without
corruption and that all parts of a multi-file sharchive have been unpacked.
The unshar utility strips off mail and news headers before passing the remainder
of its input to sh.
(1996-10-18)
Nearby terms:
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