CODEWITHSUNDEEP
cstdoutstdinstderr
user3149632
user3149632

Reputation:

Standard output/input/error file in c

Is the standard input file- stdin is always the keyboard, the standard output file- stdout is always the screen, and the standard error file- stderr is always the screen? and why?

Upvotes: 2

Views: 1328

Answers (1)

Olotiar
Olotiar

Reputation: 3274

By default, yes. But the reason that system is so flexible and powerful is that it can be redirected (by the user or the program both)

When you type in a shell

command > file

You actually redirect the stdout of command into the file file.

By doing 

command1 | command2

you redirect the stdout of command1 to the stdin of command2

Programatically, the file descriptor 0 is always stdin, 1 stdout, 2 stderr.

I suggest learning about dup and dup2 for redirecting them programatically.

Example

int file = open("out.txt", O_APPEND | O_WRONLY);
int stdout_cpy = dup(1);    // Clone stdout to a new descriptor
dup2(file, 1);              // Make file the new fd 1, i.e. redirect stdout to out.txt

Upvotes: 3

Related Questions