Question

我正在运行我在Oracle网站上找到的全双工服务器/客户端代码：

写作./fd_client哈哈哈时我会得到类似的东西：

HAHAHA0 $0

大写是好的（它应该是它应该返回的服务器）但是，我该怎么回避垃圾？

fd_client.c

#include <unistd.h>
#include <stdio.h>
#include <errno.h>
#include <ctype.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <string.h>
#include <stdlib.h>
#include <string.h>
#include <pthread.h>
#include "fullduplex.h" /* For name of the named-pipe */


int main(int argc, char *argv[])
{
    int wrfd, rdfd, numread;
    char rdbuf[MAX_BUF_SIZE];

    /* Check if an argument was specified. */

    if (argc != 2) {
        printf("Usage : %s \n", argv[0]);
        exit (0);
    }

    /* Open the first named pipe for writing */
    wrfd = open(NP1, O_WRONLY);

    /* Open the second named pipe for reading */
    rdfd = open(NP2, O_RDONLY);

    /* Write to the pipe */
    write(wrfd, argv[1], strlen(argv[1]));

    /* Read from the pipe */
    numread = read(rdfd, rdbuf, MAX_BUF_SIZE);

    rdbuf[numread] = '0';

    printf("Full Duplex Client : Read From the  Pipe : %s\n", rdbuf);

    return 0;
}

fd_server.c

#include <unistd.h>
#include <stdio.h>
#include <errno.h>
#include <ctype.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <string.h>
#include <stdlib.h>
#include <string.h>
#include <pthread.h>
#include "fullduplex.h" /* For name of the named-pipe */

int main(int argc, char *argv[])
{
    int rdfd, wrfd, ret_val, count, numread;
    char buf[MAX_BUF_SIZE];

    /* Create the first named - pipe */
    ret_val = mkfifo(NP1, 0666);

    if ((ret_val == -1) && (errno != EEXIST)) {
        perror("Error creating the named pipe");
        exit (0);
    }

    ret_val = mkfifo(NP2, 0666);

    if ((ret_val == -1) && (errno != EEXIST)) {
        perror("Error creating the named pipe");
        exit (0);
    }

    /* Open the first named pipe for reading */
    rdfd = open(NP1, O_RDONLY);

    /* Open the second named pipe for writing */
    wrfd = open(NP2, O_WRONLY);

    /* Read from the first pipe */
    numread = read(rdfd, buf, MAX_BUF_SIZE);

    buf[numread] = '0';

    printf("Full Duplex Server : Read From the pipe : %s \n", buf);

    /* Convert to the string to upper case */
    count = 0;
    while (count < numread) {
        buf[count] = toupper(buf[count]);
        count++;
    }

    /* 
     * Write the converted string back to the second 
     * pipe 
     */    
    write(wrfd, buf, strlen(buf));
}

fullduplex.h

#define NP1     "/tmp/np1"
#define NP2     "/tmp/np2"
#define MAX_BUF_SIZE    255

Answer 1

你的意思是：

rdbuf[numread] = '\0';

fd_server.c中的buf也存在同样的问题。

Answer 2

此：

buf[numread] = '0';

错了。你想要：

buf[numread] = '\0';

（与rdbuf[numread] = '0';相同。）

Answer 3

这些行产生错误输出：

buf[numread] = '0';
printf("Full Duplex Server : Read From the pipe : %s \n", buf);

首先，buf[numread] = '0';覆盖你的空终止符如果被覆盖，printf(%s)不知道在哪里停止打印。

null-terminator告诉C字符串结束的位置在你覆盖它之后，C不再知道字符串结尾的位置，并打印你的字符串“HAHAHA”，但之后会继续打印垃圾。

为什么我要把这个烟斗弄脏？

3 个答案: