使用seekg()在 C++ 语言文件处理中设置位置
seekg() 是 iostream 库中的一项函数,允许我们在文件中寻求任意位置。它主要用于设置要从 C++ 文件处理中的给定文件所提取的下一个字符的位置。
语法
istream&seekg(streamoff offset, ios_base::seekdir dir); istream&seekg(streampos position); Where, position: It is the new position in the stream buffer. offset: It is an integer value of type streamoff which represents the offset in the stream’s buffer, relative to the dir parameter. dir: It is the seeking direction. It is an object of type ios_base::seekdir that can take any offset constant value. Three direction used for offset values are: ios_base::beg = from the beginning of the stream’s buffer. ios_base::cur = from the current position in the stream’s buffer. ios_base::end = from the end of the stream’s buffer.
所需步骤和操作
Begin Open a data file for input/output operations. Add ‘TutorialsPoint’ to the file. Seek to 9 position from beginning of the file. Read the next 5 characters from the file into buffer F. End F with null character as terminator character. Print the contents. Close the file. End
示例
#include <fstream> #include <iostream> using namespace std; int main (int argc, char** argv) { fstream File("d.txt", ios::in | ios::out ); File << "TutorialsPoint"; File.seekg(9, ios::beg); char F[9]; File.read(F, 5); F[5] = 0; cout <<F<< endl; File.close(); }
输出
Point
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