STDOUT (standard output stream) and stderr (standard input stream) redirection issues

　I want to write both the message and the error message list to the same file.

1 /*2 * * Set the stream so that both the output and the error flow point to the specified file3 */4 if(OUTPUT1 = Freopen (PATH,"a", stdout)) = =NULL)5 exit (exit_failure);6     7 if(Output2 = Freopen (PATH,"a", stderr)) = =NULL)8Exit (Exit_failure);

At first, I wrote this.

" Error List: \ n " , OUTPUT1);  for 1 ; i + + )       {= i       ; " ERROR "  );}

As a result, the contents of the file are in the error message list earlier, prompting the message at the end.

I Baidu, found that the stdout flow buffer is a full buffer, stderr is not buffered, the full buffer is the buffer is full after the write, so I used setvbuf change the stdout buffer (also declare a large enough array buffer), change to not buffer, That is, add a sentence before the code.

SETVBUF (output1, buffer, _IONBF, bufsiz);

In this way, the problem is solved.

Another way is to add a sentence of fflush (OUTPUT1) after fputs; This means that the contents of the buffer are written immediately.

Finally, the results are posted, hehe

STDOUT (standard output stream) and stderr (standard input stream) redirection issues