How to fprintf on file with recursive - c

Question

I'm a newbie with recursion. How do I fopen and fclose a file in a recursive function?
void make(LINK lis, char *name, int flag, FILE *f)
{
if (lis == NULL) {
fclose(f);
}
else {
if (flag == 0) {
FILE *f = fopen(name, "w");
flag = 1;
}
else {
fprintf(f, "CODICE: %d\n", lis->d.codice);
make(lis->next, name, 1, f);
}
}
}
My goal is to recursively write "codice" --> CODE in a file.

Answer 1

Your most immediate problem is that on the first call, you open the file and then return to the main program, without processing anything. Opening the file should be a simple test, not an if-then-else.
void make(LINK lis, char *name, FILE *f)
{
if (!lis) {
fclose(f);
}
else {
if (f) {
f = fopen(name, "w");
}
fprintf(f, "CODICE: %d\n", lis->d.codice);
make(lis->next, name, f);
}
}
}

Answer 2

How do I fopen and fclose a file in a recursive function?
Be sure to do so at the same level of recursion.
Consider first how the nth and first would look separately:
void make_nth(LINK lis, FILE *outf) {
if (lis) {
fprintf(outf, "CODICE: %d\n", lis->d.codice);
make_nth(lis->next, outf);
}
}
void make_1st(LINK lis, const char *name) {
FILE *f = fopen(name, "w");
if (f) {
make_nth(lis, f);
fclose(f);
}
}
// Usage
LINK lis = ...;
make_1st(lis, codice.txt);
Now put that together. Various ways exist to do this.
void make(LINK lis, const char *name, FILE *outf) {
if (name) {
assert(outf == NULL);
FILE *f = fopen(name, "w");
if (f) {
make(lis, NULL, f);
fclose(f);
}
} else {
if (lis) {
fprintf(outf, "CODICE: %d\n", lis->d.codice);
make(lis->next, NULL, outf);
}
}
}
// Usage
LINK lis = ...;
make(lis, codice.txt, NULL);