src/process2.c

   1 #include <stdio.h>
   2
   3 /* open/read/write/close */
   4 #include <fcntl.h>
   5
   6 /** If buffer is too small to hold entire string, it is incremented by this value */
   7 #define BUFFER_STEP 16
   8
   9 /**
  10  * Program grabs data from process1, calculates number of characters in each line
  11  * and pass the value to process3.
  12  */
  13 int main(void) {
  14         /** Named pipe used to communicate with process1 */
  15         char * read_pipe = "/tmp/process1pipe";
  16
  17         /** Named pipe used to communicate with process3 */
  18         char * write_pipe = "/tmp/process2pipe";
  19
  20         /** Descriptor of input pipe */
  21         int read_descriptor;
  22
  23         /** Descriptor of output pipe */
  24         int write_descriptor;
  25
  26         /**
  27          * Buffer used for storing data from input pipe.
  28          * Data is stored in chunks of BUFFER_STEP size.
  29          * If data during reading is bigger than this value, then number of
  30          * characters is saved, and buffer is cleared for reading another chunk.
  31          */
  32         char buffer[BUFFER_STEP];
  33
  34         /** Index used when iterating buffer */
  35         int i = 0;
  36
  37         /** Stores number of bytes read from input pipe in current iteration */
  38         ssize_t count = 0;
  39
  40         /* Reading from process1 */
  41         read_descriptor = open(read_pipe, O_RDONLY);
  42
  43         /* Writing to process2 */
  44         mkfifo(write_pipe, 0666);
  45         write_descriptor = open(write_pipe, O_WRONLY);
  46
  47         int number_of_characters = 0;
  48
  49         while(1) {
  50                 /* Read data from input pipe */
  51                 count = read(read_descriptor, buffer, BUFFER_STEP);
  52
  53                 fprintf(stderr, "[%s] Fetched: %d bytes\n", "process2", count);
  54
  55                 if (count > 0) {
  56                         for (i = 0; i < count; i++, number_of_characters++) {
  57                                 if (buffer[i] == '\n') {
  58                                         fprintf(stderr, "[%s] Calculated: %d characters. Sending...\n", "process2", number_of_characters);
  59                                         write(write_descriptor, &number_of_characters, sizeof(number_of_characters));
  60                                         write(write_descriptor, '\n', 1);
  61                                         number_of_characters = 0;
  62                                 }
  63                         }
  64                 }
  65                 else {
  66                         break;
  67                 }
  68         }
  69
  70         close(read_descriptor);
  71         close(write_descriptor);
  72         unlink(write_descriptor);
  73
  74         return 0;
  75 }