c3-4 test the atrribute of the file

#include "apue.h"
#include <fcntl.h>

int
main(int argc,char * argv[])
{
    int val;

    if ( argc != 2)
        err_quit("usage: a.out ");

    if(( val = fcntl(atoi(argv[1]), F_GETFL,0)) < 0)
        err_sys("fcntl error for fd %d",atoi(argv[1]));
    switch( val &O_ACCMODE )  {
    case O_RDONLY:
        printf("read only ");
        break;
    case O_WRONLY:
        printf("write only");
        break;
    case O_RDWR:
        printf("read write ");
        break;
    default:
        err_dump("unknown  access mode ");
    }

    if (val & O_APPEND)
        printf(",append");
    if (val & O_NONBLOCK)
        printf(",nonblock");
    #if  defined(O_SYNC)
        if( val & O_SYNC )
            printf(",syschronouse writers ");
    #endif
    #if !defined( _POSIX_C_SOURCE ) &&  defined(O_SYNC)
        if (val & O_FSYNC )
            printf(",synchronous writers ");
    #endif
    putchar('\n');
    exit(0);

}