Returning multiple file pointers in C - c

Question

I'm new to C and would like some help with an issue I have. I'm reading and writing to pipes as follows:
f = fdopen(fdH2P[WRITE], "w"); // writing to pipe, returns a file pointer
and
r = fdopen(fdP2H[READ], "r"); // reading from pipe
I want to return both these file pointers from my function. What's the best way to do that?

Answer 1

You can either put the two file pointers into a structure and return that, or you can pass pointers to the function, like this
void GetPipes( FILE **wptr, FILE **rptr )
{
*wptr = fdopen(fdH2P[WRITE], "w");
*rptr = fdopen(fdP2H[READ], "r");
}
void SomeOtherFunction( void )
{
FILE *wptr, *rptr;
GetPipes( &wptr, &rptr );
...
}

Answer 2

You can return a struct:
Define struct, with typedef for convenience
typedef struct dual_fp {
FILE *read_fp;
FILE *write_fp;
} dual_fp;
Add function to open two files
dual_fp dual_fdopen(int write_fd, int read_fd) {
dual_fp ret;
// review error handling and reporting,
// such as add error code fields to struct dual_fp,
// and possibly do not open 2nd / close 1st file if the other fails
ret.write_fp = fdopen(write_fd, "w");
if (!ret.write_fp) perror("dual_fdopen for write");
ret.read_fp = fdopen(read_fd, "r");
if (!ret.read_fp) perror("dual_fdopen for read");
return ret;
}
Call it
dual_fp fps = dual_fdopen(fdH2P[WRITE], fdopen(fdP2H[READ]);
// use fps.read_fp and fps.write_fp after checking they are not NULL

Answer 3

Create a struct and return an instance of the struct.
typedef struct
{
FILE* write;
FILE* read;
} FilePointers;
FilePointers foo()
{
// Assuming you have access to the data...
FILE* w = fdopen(fdH2P[WRITE], "w");
FILE* r = fdopen(fdP2H[READ], "r");
FilePointers fp = {w, r};
return fp;
}