I was wondering the difference between
The following symbolic constants shall be defined for file streams:
File number of stderr; 2.
File number of stdin; 0.
File number of stdout; 1.
stdout is a
FILE* "constant" giving the standard outout stream. So obviously
fprintf(stdout, "x=%d\n", x); has the same behavior as
printf("x=%d\n", x);; you use
<stdio.h> functions like
STDOUT_FILENO is an integer file descriptor (actually, the integer 1). You might use it for
The relation between the two is
STDOUT_FILENO == fileno(stdout)
You usually prefer the
FILE* things, because they are buffered (so usually perform well). Sometimes, you may want to call
fflush to flush buffers.
You could use file descriptor numbers for syscalls like write(2) (which is used by the
stdio library), or poll(2). But using syscalls is clumpsy. It may give you very good efficiency (but that is hard to code), but very often the
stdio library is good enough (and more portable).
(Of course you should
#include <stdio.h> for the stdio functions, and
#include <unistd.h> -and some other headers- for the syscalls like
write. And the stdio functions are implemented with syscalls, so
fprintf may call