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Does every process have stdin, stdout and stderr associated to it to the Keyboard and Terminal?
I have a small program. I want to replace the keyboard input to a file called new.txt. How do I go about it?
FILE *file1
fopen("new.txt", "r")
close(0); // close the stdio
dup2(file1, 0);
Would this work? Now my stdio is redirected to the FILE?
No, not every process. But on operating systems that give you a command-line window to type in, a program started from that command line will have stdin connected to the keyboard, and stdout and stderr both going to the terminal.
If one program starts another, then often the second program’s standard streams are connected to the first program in some way; for example, the first program may have an open descriptor through which it can send text and pretend that it’s the “keyboard” for the second process. The details vary by operating system, of course.