程序3-4 对指定的描述符打印文件标志

/*
 ============================================================================
 Name        : test.c
 Author      : blank
 Version     :
 Copyright   : Your copyright notice
 Description : 程序3-4 对指定的描述符打印文件标志
 ============================================================================
*/

#include <stdio.h>
#include <fcntl.h>
#include <stdlib.h>
#include "ourhdr.h"

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

    if (argc != 2){
        err_quit("usage: ./test <descriptor#>");
    }

    if ((val = fcntl(atoi(argv[1]), F_GETFD, 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(", synchronous writes");
    }
#endif

#if !defined(_POSIX_C_SOURCE) && defined(O_FSYN)
    if (val & O_FSYN){
        printf(", synchronous writes.");
    }
#endif

    putchar('
');
    exit(0);
}