If I want to use a physical file along with other types of streams such as a socket, I can simply convert a file handle into a file descriptor:
#include <stdlib.h>
#include <stdio.h>
int main(void) {
FILE *f = fopen("uniquefilename.ext", "w");
int fd = fileno(f);
printf("%d\n", fd);
fclose(f);
return 0;
}
Does the GNU Standard Library provide a way to obtain a physical file's descriptor directly? Something to the effect of:
int fd = some_call("file_name.ext", "mode");
It seems I need to note I am completely aware of how a descriptor is not implicitly bound to any specific file. I was misleading when I wrote "obtain a physical file's descriptor"; what I should have wrote is something like "create a descriptor enabling access to a specific physical file".
It does not.
However, you can use the open function directly! This is part of Linux itself, not the C standard library (technically the C standard library provides a small wrapper to allow you to call it as a C function).
Example usage:
int fd = open("file_name.ext", O_RDWR); // not fopen
// do stuff with fd
close(fd); // not fclose
Note: The man page recommends including <sys/types.h>, <sys/stat.h>, and <fcntl.h>, and for close you need <unistd.h>. That's quite a few headers, and I don't know if they're all necessary.