#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; } 上述c++代码帮我同等转换成python代码

你好！以下是将上述 C++ 代码转换为 Python 代码的等效版本：

import cv2
import time

rtsp_url = "rtsp://192.168.42.142:8554/live"

def write_data_to_file(name, data):
    with open(name, "wb") as fd:
        fd.write(data)
        return len(data)
    return -1

def image_callback(handler, frmdata, frmsize, width, height, pixfmt):
    print(f"Image {frmsize}@{frmdata} -- {width}x{height} -- {pixfmt}")
    if frmdata:
        t = int(time.time() * 1000)
        if t - ts > 1000:
            ts = t
            name = f"pictures/{width}x{height}-{pixfmt}_{counter}.jpg"
            if pixfmt == 5:
                write_data_to_file(name, frmdata)

def main(rtsp_url):
    ts = int(time.time() * 1000)
    
    service = cv2.VideoCapture(rtsp_url)
    counter = 0
    
    while True:
        ret, frame = service.read()
        if not ret:
            break
        
        t = int(time.time() * 1000)
        if t - ts > 1000:
            ts = t
            counter += 1
            name = f"pictures/{frame.shape[1]}x{frame.shape[0]}-5_{counter}.jpg"
            cv2.imwrite(name, frame, [int(cv2.IMWRITE_JPEG_QUALITY), 80])
    
    service.release()
    print("done.")

if __name__ == "__main__":
    main(rtsp_url)

请注意，上述 Python 代码使用了 `cv2` 库来处理视频流和图像。确保在运行代码之前，已经安装了相应的库。此外，Python 代码中的图像保存路径 `pictures/` 需要事先存在。