#include<stdio.h> int main(int argc, char const *argv[]) { FILE *fp=fopen("1.txt","w+"); if(fp=NULL) { perror("fopen err"); return -1; } char ch[32]="hello"; fwrite(ch,sizeof(char),32,fp); char ch1[32]; rewind(fp); fread(ch1,sizeof(char),32,fp); for(int i=0;i<5;i++) { printf("%c",ch1[i]); } putchar(10); fclose(fp); return 0; }

这段代码是一个简单的文件读写程序，它打开一个名为"1.txt"的文件，并以可读写的方式打开它。如果打开文件失败，程序将输出"fopen err"并返回-1。程序将字符串"hello"写入文件中，然后将文件指针移回文件开头。接着，程序从文件中读取32个字符到数组ch1中，并输出前5个字符到控制台。最后，程序关闭文件并返回0。

需要注意的是，程序中if(fp=NULL)应该是if(fp==NULL)，因为"="是赋值操作符，而"=="才是判断相等的操作符。

相关问题

windows环境下#include <stdio.h> #include <stdlib.h> #include <string.h> #include<windows.h> #include <WinSock2.h> #define PORT 8888 int main(int argc, char const *argv[]) { int sock = 0, valread; struct sockaddr_in serv_addr; char buffer[1024] = {0}; char filename[100] = {0}; FILE *fp; // 创建 socket 文件描述符 if ((sock = socket(AF_INET, SOCK_STREAM, 0)) < 0) { printf("\n Socket creation error \n"); return -1; } // 初始化地址结构体 memset(&serv_addr, '0', sizeof(serv_addr)); serv_addr.sin_family = AF_INET; serv_addr.sin_port = htons(PORT); // 将 IP 地址从字符串转换为二进制格式 if (inet_pton(AF_INET, "127.0.0.1", &serv_addr.sin_addr) <= 0) { printf("\n Invalid address/ Address not supported \n"); return -1; } // 连接服务器 if (connect(sock, (struct sockaddr *)&serv_addr, sizeof(serv_addr)) < 0) { printf("\n Connection Failed \n"); return -1; } // 发送文件名 printf("Enter filename: "); scanf("%s", filename); send(sock, filename, strlen(filename), 0); // 打开文件 fp = fopen(filename, "rb"); if (fp == NULL) { perror("fopen failed"); exit(EXIT_FAILURE); } // 发送文件内容 while (!feof(fp)) { valread = fread(buffer, sizeof(char), sizeof(buffer), fp); send(sock, buffer, valread, 0); memset(buffer, 0, sizeof(buffer)); } // 关闭文件和 socket fclose(fp); close(sock); return 0;}该怎么写

这是一个基于 Socket 实现文件传输的客户端程序，需要连接到一个运行在本地的服务器。以下是完整代码：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <winsock2.h>

#define PORT 8888

int main(int argc, char const *argv[])
{
    WSADATA wsa;
    SOCKET sock = INVALID_SOCKET;
    struct sockaddr_in serv_addr;
    char buffer[1024] = {0};
    char filename[100] = {0};
    FILE *fp;
    int valread;

    // 初始化 Winsock 库
    if (WSAStartup(MAKEWORD(2, 2), &wsa) != 0)
    {
        printf("WSAStartup failed. Error Code : %d\n", WSAGetLastError());
        return -1;
    }

    // 创建 socket 文件描述符
    if ((sock = socket(AF_INET, SOCK_STREAM, 0)) == INVALID_SOCKET)
    {
        printf("Socket creation error. Error Code : %d\n", WSAGetLastError());
        return -1;
    }

    // 初始化地址结构体
    memset(&serv_addr, '0', sizeof(serv_addr));
    serv_addr.sin_family = AF_INET;
    serv_addr.sin_port = htons(PORT);

    // 将 IP 地址从字符串转换为二进制格式
    if (inet_pton(AF_INET, "127.0.0.1", &serv_addr.sin_addr) <= 0)
    {
        printf("Invalid address/ Address not supported.\n");
        return -1;
    }

    // 连接服务器
    if (connect(sock, (struct sockaddr *)&serv_addr, sizeof(serv_addr)) < 0)
    {
        printf("Connection failed.\n");
        return -1;
    }

    // 发送文件名
    printf("Enter filename: ");
    scanf("%s", filename);
    send(sock, filename, strlen(filename), 0);

    // 打开文件
    fp = fopen(filename, "rb");
    if (fp == NULL)
    {
        perror("fopen failed");
        exit(EXIT_FAILURE);
    }

    // 发送文件内容
    while (!feof(fp))
    {
        valread = fread(buffer, sizeof(char), sizeof(buffer), fp);
        send(sock, buffer, valread, 0);
        memset(buffer, 0, sizeof(buffer));
    }

    // 关闭文件和 socket
    fclose(fp);
    closesocket(sock);

    // 清理 Winsock 库
    WSACleanup();

    return 0;
}

需要注意的是，在 Windows 环境下使用 Socket 编程需要先调用 `WSAStartup()` 函数来初始化 Winsock 库，并在程序结束时调用 `WSACleanup()` 函数来清理 Winsock 库。此外，Windows 下使用的是 `closesocket()` 函数来关闭 socket，而不是 `close()` 函数。

#include <stdio.h> #include <iostream> #include <chrono> #include <thread> #include <DjiRtspImageSource.h> #define STB_IMAGE_WRITE_IMPLEMENTATION #include "stb_image_write.h" static inline int64_t now() { return std::chrono::duration_cast<std::chrono::milliseconds>(std::chrono::system_clock::now().time_since_epoch()).count(); } static int write_data_to_file(const char* name, uint8_t* data, int size) { FILE* fd = fopen(name, "wb"); if(fd) { int w = (int)fwrite(data, 1, size, fd); fclose(fd); return w; } else { return -1; } } char rtsp_url = "rtsp://192.168.42.142:8554/live"; int main(int argc, char** argv) { if(argc < 1) return -1; if(argc == 1) { std::cout << "Usage : " << argv[0] << " <url>" << std::endl; return -1; } int64_t ts = now(); DjiRtspImageSource service(rtsp_url); service.setImageCallback(nullptr, [&ts](void* handler, uint8_t* frmdata, int frmsize, int width, int height, int pixfmt) -> void { printf("Image %d@%p -- %dx%d -- %d\n", frmsize, frmdata, width, height, pixfmt); if(frmdata) { int64_t t = now(); if(t - ts > 1000) { ts = t; char name[64]; static int counter = 0; sprintf(name, "pictures/%dx%d-%d_%d.jpg", width, height, pixfmt, ++counter); if(pixfmt == 5) stbi_write_jpg(name, width, height, 3, frmdata, 80); } } }); service.start(); for(;;) //for(int i=0; i<30; i++) { std::this_thread::sleep_for(std::chrono::milliseconds(1000)); } service.stop(); std::cout << "done." << std::endl; return 0; } 利用上述代码实现提取并解码二维码的信息，并将解码结果保存到tta文件夹下保存为文件名为 list_of_goods,给出c++源码

以下是使用 C++ 代码从图像中提取和解码二维码信息，并将解码结果保存到名为 "list_of_goods.txt" 的文件中：

#include <stdio.h>
#include <iostream>
#include <chrono>
#include <thread>
#include <DjiRtspImageSource.h>
#include <zbar.h>

#define STB_IMAGE_WRITE_IMPLEMENTATION
#include "stb_image_write.h"

using namespace std;
using namespace zbar;

static inline int64_t now()
{
    return chrono::duration_cast<chrono::milliseconds>(chrono::system_clock::now().time_since_epoch()).count();
}

static int write_data_to_file(const char* name, uint8_t* data, int size)
{
    FILE* fd = fopen(name, "wb");
    if(fd)
    {
        int w = (int)fwrite(data, 1, size, fd);
        fclose(fd);
        return w;
    }
    else
    {
        return -1;
    }
}

void save_qr_code_data(const char* data)
{
    FILE* file = fopen("tta/list_of_goods.txt", "a");
    if (file)
    {
        fprintf(file, "%s\n", data);
        fclose(file);
    }
}

char rtsp_url[] = "rtsp://192.168.42.142:8554/live";

int main(int argc, char** argv)
{
    if(argc < 1) return -1;
    if(argc == 1) 
    {
        cout << "Usage : " << argv[0] << " <url>" << endl;
        return -1;
    }
    int64_t ts = now();

    DjiRtspImageSource service(rtsp_url);
    service.setImageCallback(nullptr, [&ts](void* handler, uint8_t* frmdata, int frmsize, int width, int height, int pixfmt) -> void {
        printf("Image %d@%p  --  %dx%d -- %d\n", frmsize, frmdata, width, height, pixfmt);
        if(frmdata)
        {
            int64_t t = now();
            if(t - ts > 1000)
            {
                ts = t;
                char name[64];
                static int counter = 0;
                sprintf(name, "pictures/%dx%d-%d_%d.jpg", width, height, pixfmt, ++counter);
                if(pixfmt == 5)
                {
                    stbi_write_jpg(name, width, height, 3, frmdata, 80);

                    // Decode QR code
                    ImageScanner scanner;
                    scanner.set_config(ZBAR_NONE, ZBAR_CFG_ENABLE, 1);
                    Image image(width, height, "Y800", frmdata, width * height);
                    int n = scanner.scan(image);
                    for (Image::SymbolIterator symbol = image.symbol_begin(); symbol != image.symbol_end(); ++symbol)
                    {
                        cout << "QR code data: " << symbol->get_data() << endl;
                        save_qr_code_data(symbol->get_data().c_str());
                    }
                }
            }
        }
    });
    service.start();
    for(;;)
    //for(int i=0; i<30; i++)
    {
        this_thread::sleep_for(chrono::milliseconds(1000));
    }
    service.stop();
    cout << "done." << endl;
    return 0;
}

注意，上述代码使用了 `zbar` 库来进行二维码解码。确保在编译和运行之前已经安装了该库，并根据需要修改保存文件的路径。同时，需要确保 "tta" 文件夹已经存在，以便保存解码结果。