OS1/smallsh/main.c

#include "main.h"

int main() {

  int status = 0;
  size_t input_size = 2048;
  size_t getline_len;
  char* input = malloc(sizeof(char) * input_size);

  while(1) {
    printf(": ");
    fflush(stdout);
    getline_len = getline(&input, &input_size, stdin);
    input[getline_len - 1] = '\0';

    // Ignore whitespace or comments
    if(input == NULL ||
       input[0] == '#') {
      continue;
    }


    char*** array = malloc(sizeof(char**));
    int num_strings = input_format(input, input_size, array);

    char* first_array = (*array)[0];

    // Built in shell commands
    if(!strncmp(first_array, "exit", 4))
        return 0;
    else if(!strncmp(first_array, "cd", 2))
      inbuilt_cd((*array)[1]);
    else if (!strncmp(first_array, "status", 6))
      printf("%d\n", status);
    else
      status = run_command(array, num_strings);
    fflush(stdout);

  }
}

int input_format(char* input, size_t input_size, char*** array) {

  const int max_args = 512;
  int num_strings = 0;
  char* pch;
  *array = malloc(sizeof(char*) * max_args);

  pch = strtok (input," ");
  while (pch != NULL)
  {
    (*array)[num_strings] = malloc(sizeof(char*) * (strlen(pch) + 1));
    strcpy((*array)[num_strings], pch);
    num_strings++;

    pch = strtok (NULL, " ");
  }

  return num_strings;
}

void inbuilt_cd(char* args) {

  if(args)
    chdir(args);
  else
    chdir(getenv("HOME"));

}

int run_command(char*** array, int num_array) {

  char* comb_string = malloc(sizeof(char) * 100);
  sprintf(comb_string, "/usr/bin/");
  strcat(comb_string, (*array)[0]);
  int f = fork();
  pid_t pid;
  if(!f) 
    pid = execv(comb_string, (*array));

  int status;
  waitpid(pid, &status, 0);

  free(comb_string);

  return status;

}