/* ********************************************************************** */
/* *									* */
/* *  FILE: 	lseek.c							* */
/* *									* */
/* *  PURPOSE:	This file contains the main routines for program #1.3	* */
/* *		in CS590 / Summer 2002.  Specifically, this file	* */
/* *		shows the use of a lseek call foloowed by a write as	* */
/* *		opposed to using the O_APPEND flag on the open syscall.	* */
/* *									* */
/* *  AUTHOR:	Richard Johnson						* */
/* *									* */
/* *  REVS:	05/29/2002 - Program Created.				* */
/* *									* */
/* ********************************************************************** */

#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <fcntl.h>
#include <stdio.h>

/* ********************************************************************** */
/* *	main - This routine opens the file "file.txt" and writes 10,000	* */
/* *		lines of text to it using the lseek to end, then write.	* */
/* ********************************************************************** */

int main(int argc, char **argv)
{
	int 	i;		/*  Loop counter */
	int	fd;		/*  File descriptor */
	int	count = 0;	/*  Seek counter */
	char 	buf[64];	/*  Write buffer */ 

	/*  Check the command line args */

	if (argc != 2)
	{
		fprintf(stderr, "usage: %s <prog id>\n", argv[0]);
		exit(1);
	}

	/*  Open the file for write, but without O_APPEND */

	if ((fd = open("file.txt", O_WRONLY | O_CREAT, 
		S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH)) < 0)
	{
		perror("open failed");
		exit(1);
	}
	
	/*  Write many lines to the file; lseek to end for each write */

	for (i = 0; i < 10000; i++)
	{
		count++;
		sprintf(buf, "Process number %s - %d\n", argv[1], count);

		if (lseek(fd, 0L, SEEK_END) < 0)
			perror("lseek failed");

		if (write(fd, buf, strlen(buf)) != strlen(buf))
			perror("write failed");
	}

	/*  Cleanup */

	exit(0);
}