c++ - Problems with execvp -

i'm trying create simple shell. here's i've done far:

#include <iostream> #include <sys/wait.h> #include <unistd.h> #include <string> #include <vector> #include <sstream>  void execute(std::vector<char *> instructions) {     auto pid = fork();     int status;      if (pid < 0) {         std::cout << "fork error occured!" << std::endl;         exit(1);     } else if (pid == 0) {         if(execvp(instructions[0], instructions.data()) < 0) {             std::cout << "command not found" << std::endl;             exit(1);         }     } else {         while (wait(&status) != pid);     } }  std::vector<char *>  splitter(std::string input) {     std::istringstream iss(input);     std::vector<std::string> tokens{std::istream_iterator<std::string>{iss},         std::istream_iterator<std::string>{}};     std::vector<char *> instructions(tokens.size());     (auto = 0; != tokens.size(); ++i) {         instructions[i] = &tokens[i][0];     }     return instructions; }  int main() {     std::string input;      while (1) {         std::cout << "[cmd]:";         getline(std::cin, input);         if (input == "exit") exit(0);         std::vector<char *> instructions = splitter(input);         execute(instructions);     }      return 0; } 

when run code , enter "ls" several times varying results:

[cmd]:ls assignment iv [cmd]:ls command not found [cmd]:ls assignment iv [cmd]:ls assignment iv [cmd]:ls command not found [cmd]:pwd /users/diveafall/library/developer/xcode/deriveddata/assignment_iv-grxcoesjdabjvoenxkaprouhexuh/build/products/debug [cmd]: 

i have no idea why happens. suppose string splitting function far ideal. can please me fix it? also, if have tips please feel free give them. i'm noob , i'll appreciate help. thank you.