arg.h

#if 0

static void
usage(const char *app)
{
    panic("\n"
        "usage: %s [options]\n"
        "\n"
        "   options:\n"
        "\n"
        "   -v,         Vebose information\n"
        "   -p <port>   Server port\n"
        "   -i <ip>     Server ip-address\n"
        "   -h,         print this help messages\n"
        "\n",
        app
    );
}
int main(int argc, char **args)
{
    const char *app_name;
    ARG_BEGIN(app_name, argc, argv){
    case 'v': verbose = true; break;
    case 'i': ip = arg_str(argv, usage(app_name)); break;
    case 'p': port = arg_ushort(arg(argv), 10); break;
    case 'h': default: usage(app_name); break;
    } ARG_END;
    return 0;
}
#endif

#define ARG_BEGIN(argv0, argc, argv) \
    for (argv0 = *argv, argv++, argc--; argv[0] && argv[0][1] && argv[0][0] == '-'; argc--, argv++) {\
        char argc_, **argv_; int brk_;\
        if (argv[0][1] == '-' && argv[0][2] == '\0')\
            {argv++; argc--; break;}\
        for (brk_ = 0, argv[0]++, argv_ = argv; argv[0][0] && !brk_; argv[0]++) {\
            if (argv_ != argv) break;\
            argc_ = argv[0][0];\
            switch (argc_)
#define ARG_END }}
#define ARGC() argc_

#define arg(argv) (brk_ = 1, argv[0])
#define arg_str(argv, x) ((argv[0][1] == '\0' && argv[1] == 0)?\
    ((x), (char *)0) : (brk_ = 1, (argv[0][1] != '\0') ?\
        (&argv[0][1]) : (argc--, argv++, argv[0])))

#include <string.h>
#include <limits.h>

static inline void
panic(const char *fmt, ...)
{
    va_list args;
    fflush(stdout);
    va_start(args, fmt);
    vfprintf(stderr, fmt, args);
    va_end(args);
    exit(EXIT_FAILURE);
}
static inline long
arg_slong(const char *s, int base)
{
    char *ep = 0;
    long n = strtol(s, &ep, base);
    if (*ep != '\0' || ep == s)
        panic("Invalid number: %s\n", s);
    return n;
}
static inline int
arg_sint(const char *s, int base)
{
    long n = arg_slong(s, base);
    if (n < INT_MIN || n > INT_MAX)
        panic("Number: %d is out of range\n", n);
    return(int)n;
}
static inline unsigned 
arg_uint(const char *s, int base)
{
    long n = arg_slong(s, base);
    if (n < 0 || n > UINT_MAX)
        panic("Number: %d is out of range\n", n);
    return (unsigned)n;
}
static inline unsigned short
arg_ushort(const char *s, int base)
{
    char *ep = 0;
    long n = arg_slong(s, base);
    if (n < 0 || n > USHRT_MAX)
        panic("Number: %d is out of range\n", n);
    return (unsigned short)n;
}
static inline double
arg_real(const char *s)
{
    char *end;
    double d = strtod(s, &end);
    if (end == s || *end != '\0')
        panic("Invalid number: %s\n", s);
    return d;
}
static inline int
arg_enum(const char *s, const char **opt, int n)
{
    for (int i = 0; i < n; i++)
        if (strcmp(opt[i], s) == 0)
            return i;
    panic("Invalid enum: %s\n", s);
    return -1;
}