Executer une commande avec exec

const char* paramList[] = {"/bin/ls", "-l", "/u/userid/dirname", NULL};
execvp("/bin/ls", paramList);

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

#define TAILLE 256
#define XSTR(X) #X
#define STR(X) XSTR(X)

int main(void)
{
  char* cmd[2];
  char chaine[TAILLE];
  int ret = 0;
  int size = 0;

  scanf("%"STR(TAILLE)"s", chaine);

  size = strlen(chaine);
  cmd[0] = malloc((size + 1) * sizeof(char));
  strncpy(cmd[0], chaine, size);
  cmd[0][size] = 0;
  cmd[1] = NULL;
  ret = execvp(chaine, cmd);
  printf("Error = %i\n", ret);
  free(cmd[0]);

  return 0;
}