List All Available filesystems in C

fslist.c

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

char** list_filesystems(size_t* len){
    char buffer[1024];
    FILE* fs = fopen("/proc/filesystems","r");
    if(fs == NULL){
        perror("Failed to open file");
    }
    char** ret = malloc(sizeof(char*));
    ret[0] = NULL;
    size_t i = 0;
    while(fgets(buffer, sizeof(buffer), fs) != NULL){
        if(strncmp(buffer, "nodev", 4)){
            buffer[strlen(buffer)-1] = '\0';
            ret = realloc(ret, sizeof(ret)+sizeof(char*)*2);
            ret[i] = strdup(buffer+1);
            i++;
        }
    }
    *len = i;
    return ret;
}

void main(){
    size_t *len;
    char** fss = list_filesystems(len);
    for(size_t i = 0; i < *len;i++){
        puts(fss[i]);
    }
}