Why fprintf with stderr ??

Question

Hi!
I'm unable to understand why I will use:
fprintf(stderr, "Error: %s", strerror(errno));

When I can use:
printf("Error: %s", strerror(errno));
And
perror("Error");

Can anyone explain?
I don't think I have to use fprintf.

And can I do something about user defined function that it's error can be printed by "perror()". I mean I want to make a custom error that can be used by strerror(errno) or perror()

Answer 1

you're not mandatory to output error message to stderr rather than stdout (default output for printf), but you are strongly advised to do so, to separate normal output from error output: this let user filter output of your program by stream ;)

Answer 2

no, because I'm not aware of how error handling is done in C... :(

Answer 3

visph
Can you help me with my second question

Answer 4

visph
Ok Thanks 😊