duplicate shell

#include <time.h>
#include <stdio.h>
#include <unistd.h>
#include <sys/wait.h>
#include <string.h>
#include <stdlib.h>
#include <sys/types.h>
#include <wordexp.h>


void execute(char *user_input)
{
    pid_t pid;
    //process gets assigned a 'lock' if you have the right key  it opens.
    int state_loc;
    if( (pid = fork()) == -1){
      printf("fork failed\n");
      exit(1);
    }
    else if(pid == 0){
        FILE *f;
        //open the file and append. Create if not there.
        f = fopen("tmp.log", "a+");
        if (f == NULL) { printf("Something is wrong");}

        struct tm *p;
        struct tm buf;
        char timestring[100];
        time_t ltime = time(NULL);
        if (NULL != (p=localtime_r(&ltime, &buf))){
          strftime(timestring, sizeof(timestring),"** %c: ", p);
          fprintf(f, "%s %s \n", timestring, user_input);
        }
        fclose(f);

        char* separator = " ";
        char* argv[64];
        int argc = 0;
        char* tmp;
        argv[argc] = strtok_r(user_input, separator, &tmp);
        while( argv[argc] != NULL){
          argc+=1;
          argv[argc] = strtok_r(NULL, separator, &tmp);
        }
        // null termination array '\0'
        argv[argc] = '\0';

      execvp(argv[0],argv);
    }
    else{
      //waiting until the lock is open; imagine state_loc as if = 0, lock, else unlock
      wait(&state_loc);
    }
}


int main ()
{
  while(1)
  {
    char user_input[1024];
    printf("recsh>> ");
    //empty the buffer right scanf
    scanf("%[^\n]", user_input);
    //calls each character in the user input, repeat until it reaches the terminating \n
    while( getchar() != '\n');
    if(strcmp(user_input, "exit") == 0){
      printf("Exiting\n");
      break;
    }
    else{
      execute(user_input);
    }
  }
  return 0;
}