Re: Question Re: Piping and Redirection

[Hans Boldt <boldt@xxxxxxxxxx>]

Tom Liotta wrote:
> To the *nix-heads:
>
> With all the back and forth that was going on over which command line is better, I'd like to ask a question about the piping and redirection on the *nix side of things. I'm familiar with the concepts, but I'm not clear on how the issue of non-streamfile manipulation would be handled by various *nix shells.
>
> That is, under QSHELL, I can pretty much pipe the output of one command into another just as I could under just about any other *nix shell. And if I don't have a particular utility, I can build my own or possibly port one so that I'll have the same utilities that are available elsewhere. Disregarding any fancy facilities some great shell might have beyond just piping and redirection, on other systems, how do basic commands/utilities such as sed and grep handle files that aren't streamfiles?
>
> That is, traditional OS/400 commands commonly wouldn't support something like piping because they generally rely on a database record format. Is it even meaningful to make comparisons outside of QSHELL?

Strictly speaking, in Unix everything is a stream file.

It's up to particular programs and applications to assign specific
meanings to the bytes that make up a file. And so, if you want to
process certain types of files intelligently, you need specific
application programs. For certain types of collections of data, like
databases and images, processing that data using a stream model
makes little sense. For example, you wouldn't want to use grep on a
database file. Instead, you'd open an SQL command prompt and search
the database using a SELECT statement. Likewise, if you wanted to
scale an image file, you wouldn't use something like sed or perl,
you'd use an X based image program, like the gimp, or a command line
utility like ImageMagick.

On the other hand, the stream model works very nicely for files
involved with programming, such as program source files and scripts,
make files, html documents, etc.

Cheers!  Hans  (4 days to go before my LOA! :-)