Usage of infile in c++

ifstream is a stream object in C used to read data from files. The method of use is as follows: Create an ifstream object and specify the file path to be opened. Open the file using the open() method. Use the >> operator to read data from a file stream. Use the eof() and fail() methods to check for error conditions. Close the file stream using the close() method.

Usage of ifstream in C

ifstream is a stream object in C used to read data from a file. It is derived from an abstract data type called file stream and provides a convenient interface for handling file input operations.

Constructor

Creating an ifstream object requires a string parameter representing the path of the file to be opened.

<code class="cpp">ifstream infile("input.txt");</code>

Open the file

Use the open() method to open the file explicitly. If open() is not called, the file must be opened explicitly before reading it using ifstream.

<code class="cpp">infile.open("input.txt");</code>

Reading data

You can use the >> operator to read data from a file stream. It reads data into variables.

<code class="cpp">int number;
infile >> number;</code>

Error handling

ifstream provides eof() and fail() methods to check error conditions. eof() checks for end of file, while fail() checks for other errors.

<code class="cpp">if (infile.eof()) {
  // 文件结束
} else if (infile.fail()) {
  // 发生错误
}</code>

Close the file

Use the close() method to close the file stream and release system resources.

<code class="cpp">infile.close();</code>

Example

Here is an example showing how to read numbers from a file using ifstream:

<code class="cpp">#include <iostream>
#include <fstream>

using namespace std;

int main() {
  ifstream infile("input.txt");

  int number;
  infile >> number;

  cout << "读取的数字： " << number << endl;

  infile.close();

  return 0;
}</code>

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