New Features for Subprocesses

• call-process and call-process-region now return a value that indicates how the synchronous subprocess terminated. It is either a number, which is the exit status of a process, or a signal name represented as a string.
• process-status now returns open and closed as the status values for network connections.
• The standard asynchronous subprocess features work on VMS now, and the special VMS asynchronous subprocess functions have been deleted.
• You can use the transaction queue feature for more convenient communication with subprocesses using transactions. Call tq-create to create a transaction queue communicating with a specified process. Then you can call tq-enqueue to send a transaction. tq-enqueue takes these five arguments:

  (tq-enqueue tq question regexp closure fn)
  

  tq is the queue to use. (Specifying the queue has the effect of specifying the process to talk to.) The argument question is the outgoing message which starts the transaction. The argument fn is the function to call when the corresponding answer comes back; it is called with two arguments: closure, and the answer received. The argument regexp is a regular expression to match the entire answer; that's how tq-enqueue tells where the answer ends. Call tq-close to shut down a transaction queue and terminate its subprocess.
• The function signal-process sends a signal to process pid, which need not be a child of Emacs. The second argument signal specifies which signal to send; it should be an integer.