analyzer.c

 /* exercise on UNIX file system */
 /* useful characters: [] # */

 # include <stdio.h>
 # include <string.h>
 # include <fcntl.h> // for O_RDONLY
 # include <stdlib.h> // for exit()

 # define errormsg(x) { puts(x); exit(1); }
 # define SIZE 1024

 int main(int argc, char * argv[])
    {
     // performing checks on input formatting
     if((argc < 2) || (argc > 3)) errormsg("Error: Improperly formatted input");
     if((argc == 2) &&  (*(argv + 1)[0] == '-')) errormsg("Error: Improperly formatted input");
     if((argc == 3) && (*(argv + 1)[0] != '-')) errormsg("Error: Improperly formatted input");

     // assigns filename
     char *filename;
     if(argc == 2) filename = *(argv + 1);
     else filename = *(argv + 2);

     // opening file
     int file = open(filename, O_RDONLY);
     if(file == -1) errormsg("Error: open() unsuccessful");

     // analysing text
     char *buffer[SIZE];
     int chars, words, lines; // variables needed
     chars = words = lines = 0;
     int res = read(file, buffer, SIZE);
     while(res)
    {
     int index = 0;
     while(index < res)
        {
         chars++;
         if(buffer[index] == '\0' || buffer[index] == ' ') words++;
         if(buffer[index] == '\0') lines++;
        }
     res = read(file, buffer, SIZE);
    }

     // printing results
     printf("Chars: %d; Words: %d; Lines: %d", chars, words, lines);
    }

 /* teacher's version: int newword = 1; checks if newword before words++, why?
  * (it does cover for double spacing, but it does not cover for consecutive spaces longer than two chars)
  * it also uses two variables each, e.g. words and tempwords, updates one, then assigns the value to the other and prints it at the end. why?
  * if(continuous) { sleep(1); lseek(file, 0, SEEK_SET); } while(continuous);
  * the external loop revolves around "continuous" (condition: argc == 3 && *(argv + 1)[0] == '-')
  * why?
  */