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From: al@ee.pitt.edu (Alan Martello)
Newsgroups: comp.lang.perl
Subject: ANSWER Re: why doesn't my usage of "while(<>)" work ?
Message-ID: <9243@pitt.UUCP>
Date: 19 Nov 90 20:49:06 GMT
References: <9231@pitt.UUCP> <10437@jpl-devvax.JPL.NASA.GOV>
Sender: news@pitt.UUCP
Reply-To: al@ee.pitt.edu (Alan Martello)
Organization: Electrical Engineering, Univ. of Pittsburgh
Lines: 54

In article <10437@jpl-devvax.JPL.NASA.GOV>,
lwall@jpl-devvax.JPL.NASA.GOV (Larry Wall) writes:
|> In article <9231@pitt.UUCP> al@ee.pitt.edu (Alan Martello) writes:
|> : what is wrong with this example ?  I want to rsh to another
|> : machine, process the output of the command, and then
|> : use "while(<>)" just like always.  
|> : 
|> : any help appreciated, please post (unless embarassing) or mail.
|> : I'm running perl PL 41 on a Sun-3 under SunOS 4.1
|> : compiled with gcc.
|> : 
|> : #! /bin/perl
|> : 
|> : #  get the host name for the rsh
|> : $host = $ENV{'HOST'};
|> : 
|> : #
|> : #  THESE NEXT THREE LINES ARE THE OFFENDING ONES
|> : #  why does this program work only when these are
|> : #  commented out ?
|> : open(WFH, "rsh $host ls |");
|> : while (<WFH>) {  print; }
|> : close(WFH);
|> : 
|> : #
|> : #  second while statement should copy stdin to stdout
|> : #
|> : while (<>) {
|> :   print;
|> : }
|> : exit;
|> 
|> Works fine for me.  Could you have something weird in your .cshrc that's
|> trying to do dialog and getting nothing from stdin?  Try
|> 
|>     open(WFH, "rsh $host ls </dev/null 2>&1 |");
|> 
|> Larry

Thanks Larry, right guess again!
the problem was an interaction (probably in .login querying
for a terminal or some such).  Anyway, either both of these open
statements fixes it (the second one may only be valid on 
my Sun).

open(WFH, "rsh $host ls </dev/null 2>&1 |");
open(WFH, "rsh $host -n ls |");

I haven't decided if this was a subtle mistake or a stupid one...

*******************************************************************
       Alan R. Martello        Electrical Engineering Dept.
        al@ee.pitt.edu           University of Pittsburgh
*******************************************************************