fmemopen_test.c

#define _GNU_SOURCE
#include <string.h>
#include <stdio.h>
#include <stdlib.h>

#define handle_error(msg) do { perror(msg); exit(EXIT_FAILURE); } while (0)

int main(int argc, char *argv[])
{
    FILE *out, *in;
    int v1, v2, v3, s;
    size_t size;
    char *ptr;

    if (argc != 2) {
        fprintf(stderr, "Usage: %s <file>\n", argv[0]);
        exit(EXIT_FAILURE);
    }

    in = fmemopen(argv[1], strlen(argv[1]), "r");
    if (in == NULL)
        handle_error("fmemopen");
    out = open_memstream(&ptr, &size);
    if (out == NULL)
        handle_error("open_memstream");
    s = fscanf(in, "%d %d %d", &v1, &v2, &v3);
    if (s == -1)
        handle_error("fscanf");
    printf("v1 = %d, v2 = %d, v3 = %d\n", v1, v2, v3);
    /* write to out */
    s = fprintf(out, "%d %d %d", v1, v2, v3);
    if (s == -1)
        handle_error("fprintf");
    fclose(in);
    fclose(out);
    printf("size = %ld; ptr = %s\n", (long)size, ptr);
    free(ptr); /* free dynamic memory allocated by kernel when open_memstream() is called */
    exit(EXIT_SUCCESS);
}