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From: ronald@robobar.co.uk (Ronald S H Khoo)
Date: Wed, 11 Dec 1991 15:48:50 -0600
Newsgroups: list.rc
In-Reply-To: <22832.692454506@golem.UUCP>
Organization: Robobar Ltd., Perivale, Middx., ENGLAND.
X-Mailer: Mail User's Shell (7.2.2 4/12/91)
To: david@golem.uucp
Subject: Re: A lighter read function
Cc: rc@archone.tamu.edu
Message-Id: <9112112148.AA05916@robobar.Co.Uk>


In article <22832.692454506@golem.UUCP> David J Fiander wrote:

> line is available on all SCO UNIX systems, and I first saw it
> on a BSD 4.2 system (I think).  Besides it is easily written:

> #include <stdio.h>

This looks wrong to me.  line(1) does not use stdio.  Where available,
line(1) should preserve the seek position of the stream so that anyone
who comes afterwards can read the rest.  Trying to fseek back there
ain't much good either, since input might come from a non-seekable
device or pipe.  Hence, line(1) must use single character reads, just
like sh(1) does (what does rc(1L) do ?).

Here is a demonstration of line(1)'s behaviour on a SCO UNIX machine:
script 'typescript' started on Wed Dec 11 21:31:34 1991
$ grep LSEEK /usr/include/sys.s
#define	LSEEK	19
$ (line > /dev/null
>  perl -e 'print syscall(19,0,0,1)."\n"'  # ie lseek(0, 0L, SEEK_CUR)
> ) < /etc/passwd
24
$ (sed 1q > /dev/null
>  perl -e 'print syscall(19,0,0,1)."\n"'
> ) < /etc/passwd
512
$ script 'typescript' ended on Wed Dec 11 21:33:10 1991

Please excuse the use of sh(1) -- I haven't had time to learn rc.
Please excuse the use of perl(1L) -- I couldn't think of another
way of executing lseek(2) from the command line ...

(BTW, David, in case anyone you know wants an "alternative" approach to
 script(1) on SCO, mine's 83 lines of perl :-)

-- 
Ronald Khoo <ronald@robobar.co.uk> +44 81 991 1142 (O) +44 71 229 7741 (H)