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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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