#define _GNU_SOURCE
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/resource.h>
#include <sys/wait.h>
#include <unistd.h>

static int child(int argc, char* argv[])
{
	char **newargv = malloc(sizeof(char*) * argc);
	if (newargv == NULL)
	{
		perror("malloc");
		return 1;
	}

	for (int i = 0; i < argc; i++)
	{
		newargv[i] = argv[i];
	}
	newargv[argc] = NULL;

	execvp(newargv[0], newargv);

	perror("execvp");
	return 1;
}

int main(int argc, char* argv[]) {
	if (argc < 2)
	{
		printf("Usage: %s [-p LD_PRELOAD] [-l LD_LIBRARY_PATH] <cmd> [cmd args]\n", argv[0]);
		printf("\tset LD_PRELOAD to ld_preload and call execvp <cmd> [cmd args]\n");
		return 1;
	}

	int status, child_val;
	struct rusage r_usage;

	int i = 1;
	for (; i < argc; i++)
	{
		// Overwrite LD_PRELOAD.
		if (strncmp(argv[i], "-p", 2) == 0)
		{
			setenv("LD_PRELOAD", argv[i+1], 1);
			i++;
		// Overwrite LD_LIBRARY_PATH.
		} else if (strncmp(argv[i], "-l", 2) == 0)
		{
			setenv("LD_LIBRARY_PATH", argv[i+1], 1);
			i++;
		} else
		{
			break;
		}
	}

	pid_t child_pid = fork();


	if (child_pid == 0)
	{
		return child(argc - i, &argv[i]);
	}
	else if (child_pid > 0)
	{
		/* Collect child */
		wait4(child_pid, &status, 0, &r_usage);
		printf("child memory usage = %ld\n", r_usage.ru_maxrss);

		 /* Get child status value */
		 if (WIFEXITED(status))
		 {
		 	child_val = WEXITSTATUS(status);
		 	exit(child_val);
		 }
	} else
	{
		perror("fork");
	}

	return 0;
}