C/stdio.h/tmpfile
tmpfile: opens a temporary binary file for read/write operations and returns a pointer to the stream
//Declaration: FILE *tmpfile(void);
//Return: returns a null pointer on failure.
#include <stdio.h>
int main(void){
FILE *temp;
if((temp=tmpfile())==NULL) {
printf("Cannot open temporary work file.\n");
exit(1);
}
}