文件读写

#include "unistd.h"
#include "fcntl.h"
#include <iostream>
using namespace std;

int main()
{
    int fd = open("test.txt",O_RDWR | O_CREAT  | O_APPEND);
    if(write(fd,"test",4)!=4){
        cout << "error" << endl;
    }
    close(fd);

    int newFd = dup(1);
    cout << "当前系统最小的fd:" << newFd << endl;
}

当前系统最小的fd:3

写文件

    FILE* file_ptr = fopen("a.txt","wb");

    if(file_ptr==NULL){
        return;
    }

    fprintf(file_ptr,"hello world\n");
    fflush(file_ptr);
    fclose(file_ptr);

读文件

    fstream fs("b.txt", ios::in);
    if(!fs){
        return;
    }

    string line;
    while (getline(fs, line))
    {
        //
    }
    fs.close();