Write(2) low level buffer

I have been looking online for hours but I guess don't know what search terms to use while trying to solve my problem. "Write" has too many connotations and I can't narrow it down. I could use help with the title of this question.

I'm writing a bunch of garbage characters after I finish writing the file, and that's not what I want of course. How do I terminate once my file is done being read?

#include <cstdlib>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <iostream>

using std::cerr;
using std::endl;

const int BUFF_SIZE = 4096;

int main (int argc, char* argv[]) {
    if (argc < 2) {
        cerr << "Usage:\t./cat FILE ..." << endl;
        return EXIT_FAILURE;
    } // if

    for (int i = 1; i < argc; ++i) {
        int fd;
        if ((fd = open(argv[i], O_RDONLY)) == -1) {
            perror(argv[i]);
            return EXIT_FAILURE;
        } // if

        char buf [BUFF_SIZE];
        int r;

        while ((r = read(fd, buf, BUFF_SIZE-1)) > 0) {
            buf[BUFF_SIZE-1] = '\0';
            if ((write(STDOUT_FILENO, buf, BUFF_SIZE)) == -1) { // the offending line
                perror(argv[i]);
                return EXIT_FAILURE;
            } // if
        } // while

        if (r < 0) {
            perror(argv[i]);
            return EXIT_FAILURE;
        } // if

        if (close(fd) == -1) {
            perror(argv[i]);
            return EXIT_FAILURE;
        } // if
    } // for
} // main