Info Catalog elisp: Process Information elisp: Processes elisp: Signals to Processes

elisp: Input to Processes

 
 36.7 Sending Input to Processes
 ===============================
 
 Asynchronous subprocesses receive input when it is sent to them by
 Emacs, which is done with the functions in this section.  You must
 specify the process to send input to, and the input data to send.  If
 the subprocess runs a program, the data appears on the standard input of
 that program; for connections, the data is sent to the connected device
 or program.
 
    Some operating systems have limited space for buffered input in a
 pty.  On these systems, Emacs sends an EOF periodically amidst the other
 characters, to force them through.  For most programs, these EOFs do no
 harm.
 
    Subprocess input is normally encoded using a coding system before the
 subprocess receives it, much like text written into a file.  You can use
 ‘set-process-coding-system’ to specify which coding system to use (
 Process Information).  Otherwise, the coding system comes from
 ‘coding-system-for-write’, if that is non-‘nil’; or else from the
 defaulting mechanism (Default Coding Systems).
 
    Sometimes the system is unable to accept input for that process,
 because the input buffer is full.  When this happens, the send functions
 wait a short while, accepting output from subprocesses, and then try
 again.  This gives the subprocess a chance to read more of its pending
 input and make space in the buffer.  It also allows filters, sentinels
 and timers to run—so take account of that in writing your code.
 
    In these functions, the PROCESS argument can be a process or the name
 of a process, or a buffer or buffer name (which stands for a process via
 ‘get-buffer-process’).  ‘nil’ means the current buffer’s process.
 
  -- Function: process-send-string process string
      This function sends PROCESS the contents of STRING as standard
      input.  It returns ‘nil’.  For example, to make a Shell buffer list
      files:
 
           (process-send-string "shell<1>" "ls\n")
                ⇒ nil
 
  -- Function: process-send-region process start end
      This function sends the text in the region defined by START and END
      as standard input to PROCESS.
 
      An error is signaled unless both START and END are integers or
      markers that indicate positions in the current buffer.  (It is
      unimportant which number is larger.)
 
  -- Function: process-send-eof &optional process
      This function makes PROCESS see an end-of-file in its input.  The
      EOF comes after any text already sent to it.  The function returns
      PROCESS.
 
           (process-send-eof "shell")
                ⇒ "shell"
 
  -- Function: process-running-child-p &optional process
      This function will tell you whether a PROCESS, which must not be a
      connection but a real subprocess, has given control of its terminal
      to a child process of its own.  If this is true, the function
      returns the numeric ID of the foreground process group of PROCESS;
      it returns ‘nil’ if Emacs can be certain that this is not so.  The
      value is ‘t’ if Emacs cannot tell whether this is true.  This
      function signals an error if PROCESS is a network, serial, or pipe
      connection, or is the subprocess is not active.
 

Info Catalog elisp: Process Information elisp: Processes elisp: Signals to Processes