Dup2 use

The header file ：

Parameters ：

dup2 It is a system call interface to help us redirect
Usage method ： hold fd_arrays[oldfd] copy to fd_arrays[newfd], Implement redirection

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principle ：
To be able to use dup2, First understand the file descriptor fd
File descriptor

The following code does not call dup2 Interface , The essence is to point to the original stdout Of fd Points to the newly opened file .

Use dup2 It's written like this .

principle ： Put the newly opened file fd copy to fd_arrays[1] Inside , Implement redirection .

Therefore use dup2 When ,