Create new files, whose name depends on a variable from the program - c

Question

I'm trying to write a program that will save "X" number of simple textfiles- however, X is determined by the user once the program has run. I can't seem to find any help on the net as to how to solve the following two things, so any tips will be massively appreciated!
1) How do I declare these textfiles at the start of the program if I don't know how many there will be?
So far, I'm used to using:
FILE* outfile;
But what I really need is:
FILE* outfile_0, outfile_1, outfile_2... outfile_X;
The solution that comes to mind looks like a loop, but I know that this won't work!
for (i=0;I<X;i++){
FILE* outfile_i // obviously, this just literally calls it "outfile_i"
}
2) How do I name them?
I want to call them simple names, such as "textfile_1, textfile_2" etc, but I don't see how that would be possible using:
outfile=fopen("C:\\textfile.txt","w");
Again, I thought perhaps making a loop (?!) but I know that this won't work:
for(i=0;i<X;i++){
outfile_i=fopen("C:\\textfile_i.txt","w");
}
There's absolutely no way of knowing what variable "X" is before running the program.
EDIT: Problem solved- I wasn't aware you could create arrays of "FILE*", thanks for all the help!

Answer 1

Something like this should work, but requires error handling and close/free operations.
FILE **outfile = malloc(sizeof(FILE*) * X);
for(i=0;i<X;i++){
char buffer[1024];
sprintf(buffer, "%s_%d.txt", "textfile", i);
outfile[i] = fopen(buffer, "w");
}

Answer 2

You have to put all your FILE * variables in an array. I would do:
char filename[80];
char number[10];
/* Allocate our array */
FILE ** files = malloc((sizeof(FILE *) * X) + 1); /* We allocate a size of X+1 because we'll have X elements + a last NULL element. */
/* Populate our array */
for (int i = 0; i < X; i++)
{
strcpy(filename,"C:\\textfile_");
itoa(i, number, 10); /* Here 10 means we use decimal base to convert the integral value. */
strcat(filename, number);
strcat(filename, ".txt");
files[i] = fopen(filename, "w");
}
files[i] = NULL; /* Here we set the last element of our array to NULL (so when we iterate over it we can stop when we encounter NULL). */
Then you can access all your files like this:
for (int i = 0; files[i] != NULL; i++)
{
FILE * current = files[i];
/* Do something with "current" here. */
}
PS: Some security checks are required:
malloc → Verify it doesn't return NULL.
itoa → Verify that output string is valid.
fopen → Verify that the file was opened.

Answer 3

you have to store your variables in some structure (an array, a list ...) and to create some strings in memory. For example :
#include <stdio.h>
#define X 5
int main() {
FILE* outfiles[X];
unsigned short i;
char fn[32];
for (i = 0; i < X; ++i) {
sprintf(fn, "outfile_%u", i);
outfiles[i] = fopen(fn, "w");
}
}

Answer 4

Try this-
char buffer[100];
FILE* outfile[X];
for(i=0;i<X;i++){
snprintf(buffer,100,"C:\\textfile_%d.txt",i);
outfile[X]=fopen(buffer,"w");
}

Answer 5

This should help you.
# include <stdio.h>
# include <string.h>
int main ()
{
char *textfile;
int i, X;
textfile = (char *) malloc (128 * sizeof (char));
FILE *fptr;
printf ("Enter the value of X: ");
scanf ("%d", &X);
for (i=1 ; i<=X ; i++)
{
sprintf(textfile, "textfile_%d.txt", i);
fptr = fopen (textfile, "w");
fclose (fptr);
}
return 0;
}