Source : Free On-Line Dictionary of Computing

shar
     
         ("Shell archive", after {ar} and {tar})
        Any of the many {Unix} programs that creates a {flatten}ed
        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)