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From: marshall@software.org (Eric Marshall)
Newsgroups: comp.unix.wizards
Subject: question on lseek behavior
Keywords: weirdo Unix system call behavior
Message-ID: <1416@software.software.org>
Date: 5 Jul 90 12:34:35 GMT
Sender: news@software.org
Reply-To: marshall@software.org (Eric Marshall)
Distribution: usa
Organization: Software Productivity Consortium, Herndon, Virginia
Lines: 41


	I was trying to use lseek to rewind to the beginning
of input (a file), but I ran into difficulties.  When I run
the program below, it outputs the file missing the first 3 characters,
as if the lseek didn't do anything, then it outputs the entire
file.  Could someone please explain why this occurs.  I eventually
found the rewind(3S) call, and it works fine.  I am running
on SunOS 4.1.

	Thanks in advance.

	seek_test.c:

		#include <stdio.h>
		#include <sys/types.h>
		#include <sys/file.h>
		
		main()
		{
		  int c;
		  FILE *infile = fopen( "seek_test.c", "r" );
		
		  c = getc( infile );
		  c = getc( infile );
		  c = getc( infile );
		
		  lseek( fileno( infile ), 0L, L_SET );
		
		  while ( ( c = getc( infile ) ) != EOF ) putchar( c );
		}


Eric Marshall
Software Productivity Consortium
SPC Building
2214 Rock Hill Road
Herndon, VA 22070
(703) 742-7153

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