Make an application that displays text at random that conforms to the specified regex

Question

OK, so in the spirit of Code-Golf, I\'m trying out something new here: Code-Bowling.

In golf, you try to get the lowest score (smallest application, mos

Answer 1

/*
 * TODO: write manpage
 */

#include 
#include 
#include 
#include 
#include 
#include 

#define ERROR_MAX   2048    /* arbitrary, must account for argv[0] */

#define MSG_SIZE    (5+9+1) /* +1 for newline, +1 for NUL */

#if defined(linux) || defined(BSD) && BSD > 199300L
extern char const *__progname;
# define progname __progname
#else
static char *progname;
#endif

typedef enum _Progerr {
    IO_ERR = 1,
    RND_ERR = 2
} progerr_t;

static const char GREET_START[5] = "Good";  /* XXX move to Makefile? */

static const char *TIMES_OF_DAY[5] = {
    "Morning",
    "Afternoon",
    "Evening",
    "Night",
    NULL
};

int main()
{
    char errbuf[ERROR_MAX];
    char msgbuf[MSG_SIZE];
    char *slash;
    const char **time_of_day;
    int fd, rnd;
    size_t greet_len;

#ifndef progname
    /* we want proper error messages */
    progname = argv[0];
    if ((slash = strrchr(progname, '/')) != NULL)
        progname = slash+1;
#endif

    /* get REAL randomness; can't trust rand(3).
     * avoid stdio, it's slow. */
#ifdef DEBUG
    write(STDERR_FILENO, "getting random data\n", sizeof("getting random data\n")-1);
#endif
    if ((fd = open("/dev/urandom", O_RDONLY)) == -1) {
        if ((fd = open("/dev/random", O_RDONLY)) == -1)
            rnd = rand();   /* last resort, for MSYS etc. */
    }

    if (fd >= 0 && read(fd, &rnd, sizeof(int)) != sizeof(int)) {
        close(fd);
        goto rngerr;
    }

    /* higher bits of rand() have better entropy */
    assert(sizeof(int) >= 4);   /* should be compile-time assert */
    rnd = (rnd >> 24) & 0x03;

    for (time_of_day = TIMES_OF_DAY; *time_of_day && rnd; time_of_day++, rnd--)
        ;
    if (!time_of_day)
        goto rngerr;

    sprintf(msgbuf, "%s %s", GREET_START, *time_of_day);
    greet_len = strlen(msgbuf);
    msgbuf[greet_len] = '\n';
    if (write(STDOUT_FILENO, msgbuf, greet_len+1) == -1)
        goto write_err;

    return 0;

rngerr:
    sprintf(errbuf, "%s: cannot get random data\n", progname);
    write(STDERR_FILENO, errbuf, strlen(errbuf));
    return (int)RND_ERR;

write_err:
    sprintf(errbuf, "%s: cannot write to stdout\n", progname);
    write(STDERR_FILENO, errbuf, strlen(errbuf));
    return (int)IO_ERR;
}