C++使用ifstream读取文件内容的示例详解
作者:小小码农Come on
这篇文章主要为大家详细介绍了C++如何使用ifstream读取文件内容的功能,文中的示例代码讲解详细,具有一定的参考价值,感兴趣的可以了解一下
测试文件如下内容:myfile.txt
Fry: One Jillion dollars.
[Everyone gasps.]
Auctioneer: Sir, that's not a number.
数据读取, 测试 。
C++中使用ifstream类实现读文件操作,代码如下:
实现了:
1、以行读取文件
2、逐个词读取文件
3、文件名正确性检测
#include <iostream> #include <fstream> #include <string> using namespace std; //读取整个文件内容到char array数组中去 void fileReadAllToCharArray() { std::ifstream file; //以只读方式打开文件 file.open("myfile.txt", std::ios::in); //指针定位到文件末尾 file.seekg(0, std::ios::end); int fileLength = file.tellg(); //指定定位到文件开始 file.seekg(0, std::ios::beg); cout << "fileLength:" << fileLength << endl; char* buffer = new char[fileLength + 1]; file.read(buffer, fileLength); buffer[fileLength] = '\0'; string contents = buffer; cout << "contents:" << contents << endl; if (buffer) { delete[] buffer; } file.close(); } //读取方式:逐行读取Line by Line, 将行读入字符数组, 行之间用回车换行区分 void fileReadToCharArray() { std::ifstream file("myfile.txt"); constexpr int LINE_LENGTH = 100; char str[LINE_LENGTH]; int lineNum = 0; while (file.getline(str, LINE_LENGTH)) { cout << "Read from line[" << ++lineNum << "] :"<<str<<endl; } cout << "file has line:" << lineNum << endl; } //读取方式:逐行读取Line by Line, 将行读入string, 行之间用回车换行区分 void fileReadToString() { std::ifstream file("myfile.txt"); int lineNum = 0; string str; while (getline(file, str)) { cout << "Read Data on Line:[" << ++lineNum<<"] :" << str <<endl; } cout << "file has line:" << lineNum << endl; } //读取方式:逐词读取Word by Word,词之间用空格划分 void fileReadWbW() { std::ifstream file("myfile.txt"); string s; while (file >> s) { cout << "Read From File[" << s <<"]"<<endl; } } //带检测文件名功能 void fileReadWithErrCheck() { string fileName = "file .dat"; std::ifstream fin(fileName.c_str()); if (!fin) { cout << "Error Opening file:[" << fileName << "]" << " for input " << endl; exit(-1); } } int main() { #if 0 char data[100]; ofstream outfile; outfile.open("myfile.txt", ios::out | ios::trunc); cout << "enter your name: "; //cin.getline(data, 100); outfile << "hello world"<<endl; ifstream infile; infile.open("myfile.txt", ios::in); cout << "read file from myfile.txta" << endl; string readData; infile >> readData; std::cout << "data:" << readData << endl; outfile.close(); #endif //读取整个文件内容到char array数组中去 fileReadAllToCharArray(); std::cout << "-----------------" << endl; //逐行读取Line by Line fileReadToCharArray(); std::cout << "-----------------" << endl; //文件逐词读取Word by Word fileReadWbW(); std::cout << "-----------------" << endl; //逐行读取Line by Line, 将行读入string分 fileReadToString(); //带检测文件名功能 fileReadWithErrCheck(); std::cout << "-----------------" << endl; }
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