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There are a wide variety of compression methods in use. You can
tell which method was used by the last one to three letters at the end of
a file. Here are some of the more common ones and what you'll need to un-
compress the files they create (most of these decompression programs can
all be located through archie).
.txt
-
.TXT
- By itself, this means the file is a document, rather than a
program.
.ps
-
.PS
- A PostScript document (in Adobe's page description language).
You can print this file on any PostScript capable printer, or use a
previewer, like GNU project's GhostScript.
.doc
-
.DOC
- Is another common suffix for documents. No
de-compression is needed, unless it is followed by
.z
- A file compressed by the Unix
pack utility. It uses Huffman coding
(which minimizes redundancy) on each byte. Type `unpack filename.z' or
`gunzip filename.z' to decompress it. This suffix was also briefly used
to indicate gzip'ed files before `.gz' was adopted.
However, some sites still use this suffix for gzip'ed files, e.g.
the EFF's FTP-server, due to local set-ups.
.Z
- This is a Unix compression method. To uncompress the file,
type `uncompress filename.Z' or `gunzip filename.Z'
and hit enter at your host system's command prompt. If it's a
text file, you can read it online by typing
`zcat file.txt.Z |more'
at your host system's command line. There is a Macintosh
`u16.zip' is an MS-DOS program that will let you download
such a file and uncompress it on your own computer. The
Macintosh equivalent program is called MacCompress (use
archie to find these).
.zip
-
.ZIP
- These indicate the file has been compressed with a common
MS-DOS compression program, known as PKZIP (use archie to
find `PKZIP204.EXE'). Many Unix systems will let you un-ZIP
a file with a program called, well, unzip.
.gz
- The GNU project's compression format. A variant of the PKZIP
format. Use `gunzip filename.gz' to uncompress.
.zoo
-
.ZOO
- A Unix, VAX and MS-DOS format. Requires the use of a program
called zoo to uncompress.
.Hqx
-
.hqx
- A Macintosh format that needs BinHex for de-coding.
.shar
-
.Shar
- A Unix format. Use unshar.
.tar
- Another Unix format, often used to glue several related
files and/or complete directory trees into one big file.
Use the `tar' command. Often, a "tarred" file
will also be compressed with the `.Z'/`.gz' method, so you first have
to use `uncompress'/`gunzip' and then `tar'.
.TAZ
-
.TGZ
- Sometimes used for compressed tar archives `.tar.Z', that are
stored on "3 letter suffix only systems" (aka MS-DOS).
.sit
-
.Sit
- A Macintosh format, requires StuffIt.
.ARC
- A DOS format that requires the use of ARC or ARCE.
.LZH
- Another DOS compression format; requires the use of LHARC.
.lz
-
.lha
- The Amiga variant of LHARC. It's the most common Amiga archiving method,
and made with the program
lha or lz.
A few last words of caution: Check the size of a file before you get
it. The Net moves data at phenomenal rates of speed. But that 500,000-byte
file that gets transferred to your host system in a few seconds
could take more than an hour or two to download to your computer if
you're using a 2400-baud modem. Your host system may also have limits on
the amount of bytes you can store online at any one time. Also, although
it is really extremely unlikely you will ever get a file infected with a
virus, if you plan to do much downloading over the Net, you'd be wise to
invest in a good anti-viral program, just in case.
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