Pipes provide a convenient communication between a parent process and a child process.

The file system provides an implementation of pipes/

Redirection ccould be combined with pipes so that ordinary input/output uses the pipes.

A simple pipe example (no redirection):

    1   
    2   /**
    3   /* p[0] and p[1] will hold file descriptors for the pipe 
    4    * p[0] descriptor is for reading
    5    * p[1] descriptor is for writing
    6    */
    7   int p[2]; 
    8   pipe(p);  /* create a pipe (assume no errors) */
    9   
   10   if ( fork() == 0 ) {
   11     char buf[80];
   12     close(p[1]);  /* Child will only read from, not write to the pipe */
   13     while( read(p[0], buf, 80) > 0 ) {
   14       /* use data from the parent */
   15     }
   16     exit(0);
   17   } else {
   18     char buf[80];
   19     close(p[0]);  /* Parent will only write to, not read from the pipe */
   20     int more_data_to_write = 1;
   21     while(more_data_to_write) {
   22       /* generate data in buf */
   23       ...
   24       write(p[1], buf, 80);
   25       more_data_to_write = moreData();
   26     }
   27   }