hook getenv function with LD_PRELOAD

hook_getenv.c

// ltrace seems to be failing when getenv is called by shared object
// gcc -shared -fpic -ldl -o hook_getenv.so hook_getenv.c 

#define _GNU_SOURCE
#include <stdio.h>
#include <stdlib.h>
#include <dlfcn.h>
#include <limits.h>
#include <errno.h>
#include <sys/stat.h>
#include <fcntl.h>

char* (*original_getenv_func)(const char *) = NULL;

char* getenv(const char *name)
{
    if(!original_getenv_func)
        original_getenv_func = dlsym(RTLD_NEXT, "getenv");

    char* result = original_getenv_func(name);
    if(result==NULL)
        printf("%s=NULL\n", name);
    else
        printf("%s=%s\n", name, result);

    return result;
}