From: gwtmp01@...
Date: 2006-09-29T00:12:45+09:00
Subject: Re: how to determine if pipe is given


On Sep 28, 2006, at 1:03 AM, Robert Dober wrote:
> Ara's idea is how it is done in Unix, I do not know why he got so much
> critisized for it :(

Actually I think the 'normal' thing in Unix is to simply do blocking  
reads
from stdin if there are no file arguments.  This is exactly what ARGF  
does.
It is decidedly non-standard to *require* the use of a sentinel such
as '-' (or even better /dev/stdin) to cause a program to read from  
stdin.
And I believe this is what the OP is looking for.  I just don't think it
makes a lot of sense.  For example, standard input redirection would  
have
to be done as:

	program - < /some/file/to/read

which is strange.  Pipes also:

	source | program -

In both cases if you leave off the '-' the program will report an error
rather than reading and processing the data.  The next programmer
who comes along is going to be very confused by this behavior.

Can anyone think of a standard Unix program that will *only* read from
stdin in if you give an explicit sentinel as a file argument?


Gary Wright