/* fgets:  get at most n chars from iop */
char *fgets(char *s, int n, FILE *iop)
{
    register int c;
    register char *cs;

    cs = s;
    while (--n > 0 && (c = getc(iop)) != EOF)
        if ((*cs++ = c) == '\n')
            break;
    *cs = '\0';
    return (c == EOF && cs == s) ? NULL : s;
}