writer.c

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

 # include <stdio.h>
 # include <string.h>

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

 int main(int argc, char * argv[])
    {
     int current, previous; // current and previous chars/bytes? read
     char *buffer[BUFFER];
     int result = read(0, buffer, BUFFER); // reads everything that can be stored FROM STDIN
     while(result) // loops for as long as there is data to read
    {
     current = 0;
     previous = 0;
     do {
         previous = previous + current;
         result = write(1, &buffer, result - previous); // writes everything TO STDOUT
    } while(current + previous < result); // ... until the space runs out
     result = read(0, buffer, BUFFER); // begins reading again
    }
    }
 // why current + previous < result? can't all chars/bytes be written just by using:
 // result = write(1, &buffer, BUFFER) ?