NetNews Usenet Archive 1992 #31/NN_1992_31.iso/spool/comp/os/msdos/programm/11577

Internet Message Format | 1992-12-22 | 3.0 KB

Path: sparky!uunet!usc!chaph.usc.edu!aludra.usc.edu!not-for-mail
From: [e-mail] (Alex Liu)
Newsgroups: comp.os.msdos.programmer
Subject: Re: Normal MSDOS multitasking!
Date: 22 Dec 1992 10:13:10 -0800
Organization: None to Speak of
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Hi,
  I think what some people are missing is what is the idea of pipes.
Under Unix, the concept of Pipes comes from the idea of linking small
prewritten utilities to get something done as opposed to writing a
entirely new application.

For example, let say, I want to display all the files in a UNIX directory
that were created on a certain date, I also want to only display the filenames
and in reverse sort order in columns.  One way to do it under Unix is:

ls -l | grep 'Aug 12 1990' | cut -c65- | sort -r | pr -t -4

(This is an example. May not work exactly right, but it will with some tweaking
depending on the version of Unix you are using)

Now, doing something like that, as cryptic and complicated that it might look
to the uninitated, it is MUCH MUCH better than writing a "ls" (or DIR) program
that will do EVERYTHING under the sun.

You will be asking by now, what does this have to do with MS-DOS pipes?
Well, this is just to illustrate a point.  A previous poster was arguing that
doing:
    zcat file.tar.Z | tar tvf - | grep foo
is bad design, because you shouldn't have to do a compress just to find a file.
But the point is that when they designed zcat/compress and tar, it was to
be modular.  compress is a generic file compressor, that you could use with
any utility.  The fact that you have pipes allows you to use compress
without having to write your own LZW compression routines.
    unzip -v file.zip foo*.*
Doing that, for you is fine, but it is not necessarily better.  It is just
a different way to do things.  One could argue for example, that unzip is
a more complicated program than any of the unix equivalents, and at the
same token not as flexible.  For example, the 3 previous commands, you
can also grep for files of certain size, certain date, etc.  By adding
an extra command you could also sort them in reverse order or by size,
etc.  If unzip was to accomplish all that flexibility, that would make
the program much bigger.  If later, someone invents a new algorighm to
make 1000:1 compression, you could still use tar, just replace zcat with
your new compression program, but you will have to modify unzip (or wait
until PKWare makes a new version).


--
_____________________________________________________________________________
Alejandro Liu           |EMail: [e-mail] |All mispellings are intentional
1551A Ridgecrest Apt A  |Voice: 213-264-9400 |Anything mentioned here is not
Monterrey Park, CA91754 |                    |necessarily true.