/* File copy program. Error checking and reporting is minimal. */
/* From Andrew S. Tanenbaum, _Modern_Operating_Systems 3/e, p. 266. 
 * Transcribed by Janet Davis, October 8, 2010.
 */

#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdlib.h>
#include <unistd.h>
#include <stdio.h>
#include <string.h>
#include <libgen.h>
#include <errno.h>

int main(int argc, char *argv[]);	/* ANSI prototype */

#define BUF_SIZE 4096			/* use a buffer size of 4096 bytes */
#define OUTPUT_MODE 0700		/* protection bits for output file */

int main(int argc, char *argv[]) 
{
    int in_fd, out_fd, rd_count, wt_count;
    char buffer[BUF_SIZE];
   
    if (argc != 3) exit(1);		/* syntax error if argc is not 3 */

    /* Open the input file and create the output file */
    in_fd = open(argv[1], O_RDONLY);	         /* open the source file */
    if (in_fd < 0) exit(2);		 /* if it cannot be opened, exit */
    out_fd = creat(argv[2], OUTPUT_MODE); /* Create the destination file */
    if (out_fd < 0) exit(3);		/* if it cannot be created, exit */
   
    /* Copy loop */
    while (1) {
        rd_count = read(in_fd, buffer, BUF_SIZE); /* read a block of data */
    if (rd_count <= 0) break;	    /* if end of file or error, exit loop */
        wt_count = write(out_fd, buffer, rd_count);         /* write data */
        if (wt_count <= 0) exit(4);           /* wt_count <= 0 is an error */
    }

    /* Close the files */
    close(in_fd);
    close(out_fd);
    if (rd_count == 0)				 /* no error on last read */
        exit(0);
    else              				    /* error on last read */
        exit(5);
}