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10.002 What are ShrinkIt (.SHK) files and how do I use them?




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This article is from the Apple II Csa2 FAQ, by Jeff Hurlburt with numerous contributions by others.

10.002 What are ShrinkIt (.SHK) files and how do I use them?

        ShrinkIt files are the Apple II world's answer to .ZIP files in PC-ville.
An .SHK file is a file which contains one or more files which are almost always
in compressed form. Usually, they are produced by GS-ShrinkIt (also called
"GSHK" or "ShrinkIt-GS") or the Balloon NDA, or by 8-bit ShrinkIt. Some .SHK
files are produced by Macs; these may not always be compatible with A2 ShrinkIt
programs.

     An .SHK file can be unshrinked by ShrinkIt even if it shows up on the
Apple II with a TXT or BIN filetype and even if the name does not end with
".SHK" or ".shk". If a ShrinkIt file does not show up as available for
unshrinking, you can toggle an "All files" option to see the file and then
select it. If an .SHK file has a Binary II header, ShrinkIt will automatically
remove it and assign the correct filetype. (Of course, this will usually be
SHK.)

     Other kinds of ShrinkIt files include .SEA and .SDK.  An Apple II .SEA
file is a IIgs executable self-extracting archive-- i.e. you can click it on
the GS Finder and it will unShrink. There are also Mac .SEA files and these are
not GS-compatible.

     A ShrinkIt whole-disk archive is an .SHK file which is usually labeled
".SDK" to show that it is a Shrinked diskette. An .SDK file can archive a 3.5"
diskette (both sides) or 5.25" diskette (one side). Most are archives of 5.25"
DOS 3.3 diskettes produced by 8-bit ShrinkIt.

     A whole-disk ShrinkIt archive retains all data bytes on a diskette,
including files, Catalog/Directory sectors, empty tracks, and DOS if present.
An .sdk file of a DOS 3.3 5.25" disk created by 8-bit ShrinkIt also preserves
volume number-- important for some games and utilities which depend upon volume
numbers to identify disks. (5.25" whole-disk archives created by GS-ShrinkIt do
not preseve volume number.)

     8-bit/IIe ShrinkIt can be used to fully unshrink any Apple II .SHK file
except .SHK files which contain files with GS/OS resource forks and .SEA
files. For this reason, 8-bit ShrinkIt should not be used to unshrink .SHK file
archives containing GS programs unless you know that none of the contained
files has a resource fork.

     GS-ShrinkIt can handle nearly all kinds of Apple II .SHK and .SDK files.
It will not handle shrinked 5.25" DOS 3.3 .SDK files created by 8-bit ShrinkIt.
In fact, most users automatically use 8-bit ShrinkIt to create and unshrink
.SDK files of old 5.25" wares. (Balloon does not currently support whole-disk
archives.)

     Naturally, things are somewhat more crowded on 64K Apple II's. On these
machines, the functions are separated. SHRINK creates .SHK files and UNSHRINK
unshrinks them.

     On a PC, the utility NuLib (v3.24) lets you view contents and unshrink
most kinds of .SHK files. (There is a handy option to unshrink and convert
Apple II text files to PC text format.) It will not unshrink IIgs files with
resource forks.

     Here is a simple one-line batch (text) file program for easily viewing the
contents of .shk files you download to a PC (just double-click on the file
name):

c:\nulib\nulib v %1 |more

The above is for NuLib.exe located in folder c:\nulib . Save the text as
nulibv.bat in c:\nulib and tell Windows to use c:\nulib\nulibv.bat as the
'application to perform action' for doing an Open. (You do this by selecting
View--Options in the My Computer window and editing the file type info for .shk
files.)

     NuLib can also convert 5.25" .SDK files into .PO (ProDOS order) disk
images which can be used by Apple II emulators. This works for .SDK files
produced by 8-bit ShrinkIt but not for those produced by GS-ShrinkIt.

     The unshrinking process is very speedy and the size of a compressed
ShrinkIt file is, often, around half that of the original files it contains.
This makes .SHK files very handy for archiving your software. And, since a
ShrinkIt file also preserves filetype information of contained files, ShrinkIt
has become the preferred format for uploading and storing Apple II files on the
internet.

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