Re: Question Re: Piping and Redirection

Dennis

well that answers that then :)

I guess unix administrators accept that if they look at a garbage file - or
more correctly a file that will output apparent garbage - they will get
garbage in their output.. say by cat-ing a database file from oracle (I'm
guessing here) whereas an AS/400 administrator says.. well obviously the
command was not designed for that object type and accepts the rejection :)

Thanks for the education: I can see a case for both points of view !

Regards
Evan Harris

Hi, Evan:

The quick answer to your question is that the utilities can read any file
that exists on a readable filesystem within a unix system (assuming proper
authority, of course).

If I have a linux system on an Intel platform with some ext2, ext3, VFAT,
FAT and MINIX partitions (maybe throw in a couple of NFS from disparate
systems, including WIN and MAC machines), I can treat them all as equals...
every program that can read a file, can read all the files on all of those
filesystems, without regard to whether it's of a a certain type.  The
concept of treating a file differently just because it's on a different
filesystem is completely foreign to Unix, and far from what would be
considered "acceptable" in most environments.

HTH
Dennis





Evan Harris <spanner@ihug.co.nz>@midrange.com on 11/20/2002 01:31:42 AM

Please respond to midrange-l@midrange.com

Sent by:    midrange-l-admin@midrange.com


To:    midrange-l@midrange.com
cc:
Subject:    Re: Question Re: Piping and Redirection


Hi James
some responses in line...

>Well that isn't how a unix person would expect it to work.  As Hans said,
>cat doesn't care what the file is, it just opens it and reads it.  While I
>suppose there is an argument to be made that the AS/400 way is how cat
>should work (i.e. not opening files that don't make sense to show on the
>display) it is inconsistent with the way cat works on every other system.
>A unix person might choose to do this instead of DSPPFM:
>
>cat /qsys.lib/mylib.lib/myfile.file/member.mbr | more
>
>But if cat won't open the dang file that is never a possibilty.

My take is that /qsys.lib should be viewed as a different file system and
therefore we can expect some different results and behaviours. I am not as
immersed and experienced with Unix as you are so I cannot say whether every
file system accessible or mountable under unix will honour every unix
command initiated against files on that mounted file system: you or someone
more knowledgeable may be able to offer a perspective.

My knee jerk reaction is that they wouldn't , but since most of them would
be similar enough in nature- like windows - or other unixes this may not
make a difference either way. The as/400 is likely to be the odd man out
here which will make it an "as/400 thing" in the minds of those already
unable to deal with a system that can not only natively provide a unix file
system but run a "foreign" OS natively on the box :)

>Before too many people clamor that the cat method is a stupid replacement
>for DSPPFM, remember that there is an easy way to view new records *as
>they are added* to the database using unix tools (if the AS/400 used the
>tools correctly).  On unix you can do:
>
>tail -f /the/file/you/want/to/watch
>
>this works on binary or any type of file.  It just prints on the screen
>the "tail" end of the file.  The '-f' makes new entries to the print to
>the screen as they happen.  There is no way to do this on the AS/400.  You
>can use DSPPFM and go to the bottom, then exit, then do it again, etc.
>But it is not the same ability.  If the AS/400 let cat, tail, etc. work
>like they do on other systems then what I describe above would become a
>possibilty.

I have run the tail command under qshell and it worked OK although I could
not quite imagine a use for it. I am assured by my unix colleagues that it
is extremely useful but I confess to not being able to dream of an
applicable situation regarding a database file. If I really wanted to know
when a process was ended for instance I would submit a job to the job queue
to send me either a page or a break message.

I am still at a loss as to why it is useful to see records "as they are
added" to the database. My mates made exactly the same claim as you BTW and
I am no more enlightened as to what benefits this confers. Straighten me
out :)

Admittedly I was only able to run it on stream files in the IFS - IIRC I
got an operation not allowed for type of file or something similar for a
database file in /qsys.lib but as I said this makes a certain perverse
sense to me.

Hope this is interesting

Regards
Evan Harris

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