基础Shell解析代码实现

// pseudo-code for implementing a basic shell 
      
char** build_argv(char* input):
  initialize int index to 0;
  create char **argv equal to (char**) malloc(sizeof(char*));
  create char * copy equal to (char*) malloc(sizeof(char)*strlen(input)));
  call strncpy(copy, input, strlen(input));
  create char* token equal to strtok(copy, " ");
  while (token is not NULL):
    set argv[index] equal to  (char*) malloc(sizeof(char)*strlen(token)+1));
    call strncpy(args[index], token, strlen(token)+1);
    increment index by one;
    set token equal to strtok(NULL, " ");
    set argv equal to (char**) realloc(argv, sizeof(char*) * (index+1));
  set argv[index] to NULL;
  return argv;


void parse_input(char* input, int IS_FORKING):
  // Processing file descriptors first 

  initialize char in to "<";
  initialize char out to ">";
  initialize char pipe to "|";
  if ((strstr(input, &in)) != NULL):
    initialize char[] splitArgs with split(input, in);
    initialize int newstdin with open(splitArgs[1], O_RDONLY);
    call close(0);
    call dup(newstdin);
    call close(newstdin);