#include <stdio.h>
#include <fcntl.h>
#include <unistd.h>

int main(int argc, char *argv[]) {
    char buf[1024];
    int n;
    int fd;

    if (argc == 1) {
        while ((n = read(STDIN_FILENO, buf, sizeof(buf))) > 0) {
            write(STDOUT_FILENO, buf, n);
        }
        return 0;
    }

    for (int i = 1; i < argc; i++) {
        fd = open(argv[i], O_RDONLY);
        if (fd < 0) {
            perror(argv[i]);
            continue;
        }

        while ((n = read(fd, buf, sizeof(buf))) > 0) {
            write(STDOUT_FILENO, buf, n);
        }
        close(fd);
    }
    return 0;
}