C++之string流与文件流

我在人间贩卖青春2026-02-12 18:00

istrstream和ostrstream在98标准中废弃，取而代之的是istringstream和ostringstream，实现类似于C语言中sprintf和sscanf的效果

cpp 复制代码

#include <iostream>
#include <cstdio>
#include <sstream>
using namespace std;
int main(void){
    int i = 1234;
    double d = 56.78;
    char s[] = "hello";
#if 0
    char buf[100] = {0};
    sprintf(buf, "%d %lf %s", i, d, s);
    printf("%s\n", buf);
    char str[] = "100 1.23 world";
    sscanf(str, "%d %lf %s", &i, &d, s);
    printf("%d %lf %s\n", i, d, s);
#endif
    ostringstream oss;
    oss << i << ' ' << ' ' << d << ' ' << s;
    cout << oss.str() << endl;
    
    istringstream iss;
    iss.str("100 1.24 world");
    iss >> i >> d >> s;
    cout << i << ", " << d << ", " << s << endl;
    return 0;
}

文件流

C++将文件看成是一个个字符在磁盘上的有序集合，用流来实现文件的读写操作
C++中用来建立流对象的类有ifstream(输入)、ofstream（输出）、fstream（输入输出）

cpp 复制代码

#include <iostream>
#include <fstream>
using namespace std;
int main(void){
    int i = 1234;
    double d = 56.78;
    char s[] = "hello";
    ofstream ofs("a.txt");
    ofs << i << d <<s << endl;
    ofs.close();
    
    ifstream ifs("a.txt");
    int i2;
    double d2;
    string s2;
    ifs >> i2 >> d2 >> s2;
    cout << i2 << endl;
    cout << d2 << endl;
    cout << s2 << endl;
    return 0;
}