NetNews Usenet Archive 1992 #26/NN_1992_26.iso/spool/comp/lang/perl/6907

Text File | 1992-11-09 | 1.3 KB | 44 lines

Newsgroups: comp.lang.perl
Path: sparky!uunet!ferkel.ucsb.edu!taco!rock!stanford.edu!agate!spool.mu.edu!sgiblab!sgigate!sgi!wdl1!wdl39!mab
From: [e-mail] (Mark A Biggar)
Subject: Re: Bug or feature ?
Message-ID: <[e-mail]>
Sender: [e-mail]
Organization: Loral Western Development Labs
References: <[e-mail]>
Distribution: comp
Date: Mon, 9 Nov 1992 18:47:24 GMT
Lines: 31

In article <[e-mail]> [e-mail] (Lionel Cons) writes:
>I want to read the first two bytes of STDIN and then exec another
>process that uses the remaining chars from STDIN. According to the man
>pages the following script should work (if STDIN does not have the
>close-on-exec flag set):
>#!/usr/local/bin/perl
>$c1 = getc(STDIN);
>$c2 = getc(STDIN);
>print "First chars: '$c1' and '$c2'\n";
>exec('/bin/wc', '-c');
>It does not work (wc reply is 0), why ?

BUFFERING

getc uses stdio, so when you did the first getc, stdio slurped in at least
the whole first line into the buffer maybe more.  You are going to have to use
sysread to do what you want. E.G.

#!/usr/local/perl
sysread(STDIN,$c1,1);
sysread(STDIN,$c2,1);
print "First chars: '$c1' and '$c2'\n";
exec('/bin/wc', '-c');

--
Perl's Maternal Uncle
Mark Biggar
[e-mail]