simple cp program

/* File copy program. Error checking and reporting is minimal. */
#include <sys/types.h> /* include necessary header files */
#include <fcntl.h>
#include <stdlib.h>
#include <unistd.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 (TRUE) {
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
exit(5); /* error on last read */
}