#include <sys/ioctl.h>
#include <stdio.h>

main(argc, argv)
int argc;
char **argv;
{
    struct sgttyb sgo, sgn;
    struct tchars tco, tcn;

    if (argc < 2) {
        fprintf(stderr, "Usage: %s file [file ...]\n", *argv);
        exit(1);
    }

    /*
     * In real life we'd check the return values of
     * these, since if the input is redirected from
     * a file they will fail.  We are assuming the
     * terminal is always connected to the standard
     * input.
     */
    ioctl(0, TIOCGETP, &sgo);
    ioctl(0, TIOCGETC, &tco);

    sgn = sgo;
    sgn.sg_flags &= ~ECHO;      /* turn off ECHO   */
    sgn.sg_flags |= CBREAK;     /* turn on CBREAK  */

    tcn = tco;
    tcn.t_intrc = -1;           /* disable int key */

    /*
     * Set the new modes.  Again we ignore return
     * values.
     */
    ioctl(0, TIOCSETP, &sgn);
    ioctl(0, TIOCSETC, &tcn);

    while (--argc)
        more(*++argv);

    /*
     * Reset the old tty modes.
     */
    ioctl(0, TIOCSETP, &sgo);
    ioctl(0, TIOCSETC, &tco);

    exit(0);
}

/*
 * more--display the file.
 */
more(file)
char *file;
{
    FILE *fp;
    int line;
    char linebuf[1024];

    if ((fp = fopen(file, "r")) == NULL) {
        perror(file);
        return;
    }

    /*
     * Print 22 lines at a time.
     */
    for (;;) {
        line = 1;
        while (line < 22) {
            /*
             * If end-of-file, let them hit a key one
             * more time and then go back.
             */
            if (fgets(linebuf, sizeof(linebuf), fp) == NULL) {
                fclose(fp);
                prompt();
                return;
            }

            fwrite(linebuf, 1, strlen(linebuf), stdout);
            line++;
        }

        prompt();
    }
}

/*
 * prompt--prompt for a character.
 */
prompt()
{
    char answer;

    printf("Type any character for next page: ");
    answer = getchar();
    putchar('\n');
}