Lets say I have opened two tabs in the konsole (Tab1 and Tab2).
When I run tty in both of them I have:
Tab1:
~$ tty
/dev/pts/23
Tab2:
~$ tty
/dev/pts/24
If I run a simple program hello.c with a printf("Hello") in Tab1, how the system goes from writing to the stdout (file id 1) to writing to /dev/pts/23, being read by the konsole and then appearing in Tab1?
How the system know it has to give the "Hello" string to /dev/pts/23 and not to /dev/pts/24? And how it does that?
Is there a parameter given by the bash to the program so it knows which psudoterminal to send the "Hello"? Or the program sends the string back to the bash (how?) who knows to which pseudoterminal to send the data?
Thank you for your help
If you look at your process open files, you can see that the STDOUT,STDERR, etc points to the specific psuedo terminal that you already figured out using tty in your question
root@hello:~# ls -l /proc/self/fd
total 0
lrwx------ 1 root root 64 May 21 02:18 0 -> /dev/pts/3
lrwx------ 1 root root 64 May 21 02:18 1 -> /dev/pts/3
lrwx------ 1 root root 64 May 21 02:18 2 -> /dev/pts/3
As you might know, a process is created by a fork system call that actually duplicates the open file descriptors from the parent. so basically, your process gets the file descriptors from its parent.
How did the parent hot these associated with him ? well, konsole already dealt with that.