Description:
第六個作業為 8.10, page 299.
也就是作 asynchrous read, and asynchrouns write. 主要程式就作 `讀 stdin, 寫 stdout' 的動作, 直到 EOF 為止.
執行的過程可能為:

  $ ./a.out  infile  outfile    <----- copy infile to outfile
  hello i'm klim                       with async read and async write
  hello i'm klim          <---- read stdin and echo it to stdout ...
  ...
  ...
  [Copy completed]        <------ when the copy is completed, show something 
  ..                              to screen
  ..
  ^D
  $

為了模擬 slow device, 我改寫了課本的 periodicasterisk.c, 使之能每秒作 n (argv[1]) 次讀寫的動作, 每次皆從 stdin 讀一個字完, 再將之寫到 stdout. ( 程式 ) 透過 FIFO, 此程式可與這次作業互動如下:

  1st shell:
     $ periodicchars 12  < FIFO
     ....... <---- the contents of infile is shown here 
                   in the rate of 12 chars per second


   2nd shell:
     $ ./a.out infile FIFO     <-----   the contents of infile is sent to FIFO
     hello klim
     hello klim 
     .......

deadline: 5/07, 00:05 am