CS 456 - Systems Programming Spring 2024

Displaying ./code/shellv4/shellfunctions.c

#include "shell.h"


void run_shell(void){

  //some declarations
  char *line;
  char **args;
  char wd[SIZE];
  int status;

  do{

    printf("mysh: %s> ", getcwd(wd, SIZE));
    line = readLine();
    args = splitLine(line);
    status = execute(args);

  } while(status);

}

char *readLine(void){

  char *line = NULL;
  size_t bufsize = 0;

  //getline allocates a buffer for us
  if(getline(&line, &bufsize, stdin) == -1){
    if (feof(stdin)){ //we hit EOF
      exit(0); 
    } else {
      perror("readLine");
      exit(-1);
    }
  }

  return line;

}

char **splitLine(char *line){

  int bufsize = TOKBUF;
  int position = 0;
  char **tokens = malloc(bufsize * sizeof(char*));
  char *token;

  if(!tokens){
    perror("splitLine: allocation error before while loop");
    exit(-1);
  }

  token = strtok(line, TOKDELIM);
  while(token != NULL){
    tokens[position] = token;
    position++;

    if(position >= bufsize){
      bufsize += TOKBUF;
      tokens = realloc(tokens, bufsize* sizeof(char*));
      if(!tokens){
        perror("splitLine: allocation error in while loop");
        exit(-1);
      }
    }
    token = strtok(NULL, TOKDELIM);
  }

  tokens[position] = NULL;
  return tokens;
}

int launch(char **args){

  pid_t pid;
  int status;

  pid = fork();

  if(pid == 0){
    //child process
    if (execvp(args[0], args) == -1){
      perror("execute: Error in Child Process");

    }
    exit(-1);

  } else if (pid < 0){
    perror("execute: Error forking");
  } else {
    //parent process
    do {
         waitpid(pid, &status, WUNTRACED);
    } while (!WIFEXITED(status) && !WIFSIGNALED(status));

  }

  return 1;

}