From: Yohanes Santoso <ruby-talk@...>
Date: 2002-06-16T09:51:45+09:00
Subject: Re: Question: how to  do (repeated) bidirectional communication with another process via stdin/stdout ?


ke = IO.popen("cat","r+")
loginCall = "blablabla\n" # cat needs \n at the end before it echoes back the line
sysInfoCall = "fofofofo\n"

if (ke != nil)
  ke.syswrite(loginCall)

  # #flush() is not needed if you use syswrite, as #flush only flushes
  # ruby's internal buffering and ruby does not perform any buffering
  # with syswrite and sysread
  #ke.flush() 

  
  # #each("\n") blocks until it finds \n or EOF.
  #ke.each("\n") { |line| puts(line) }

  # if you don't know the number of lines to be read, then you have to use
  # IO#select so your program does not block unnecessarily.
  # alternatively if you now the number of lines to be read, just invoke
  # #readline that many times.
  puts ke.readline
  
  ke.syswrite(sysInfoCall)
  #ke.flush() # ditto, syswrite does not require flush
  
  ke.close_write

  # the #each here works because the condition \n or EOF is true.
  ke.each("\n") { |line| puts(line) }

  ke.close
end