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(elisp)Input to Processes

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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.  The
data appears on the "standard input" of the subprocess.

   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
(Note: Process Information).  Otherwise, the coding system comes from
`coding-system-for-write', if that is non-`nil'; or else from the
defaulting mechanism (Note: 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.

 - Function: process-send-string process-name string
     This function sends PROCESS-NAME the contents of STRING as
     standard input.  The argument PROCESS-NAME must be a process or
     the name of a process.  If it is `nil', the current buffer's
     process is used.

     The function returns `nil'.

          (process-send-string "shell<1>" "ls\n")
               => nil
          
          
          ---------- Buffer: *shell* ----------
          ...
          introduction.texi               syntax-tables.texi~
          introduction.texi~              text.texi
          introduction.txt                text.texi~
          ...
          ---------- Buffer: *shell* ----------

 - Function: process-send-region process-name start end
     This function sends the text in the region defined by START and
     END as standard input to PROCESS-NAME, which is a process or a
     process name.  (If it is `nil', the current buffer's process is
     used.)

     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-name
     This function makes PROCESS-NAME see an end-of-file in its input.
     The EOF comes after any text already sent to it.

     If PROCESS-NAME is not supplied, or if it is `nil', then this
     function sends the EOF to the current buffer's process.  An error
     is signaled if the current buffer has no process.

     The function returns PROCESS-NAME.

          (process-send-eof "shell")
               => "shell"

 - Function: process-running-child-p process
     This function will tell you whether a subprocess has given control
     of its terminal to its own child process.  The value is `t' if
     this is true, or if Emacs cannot tell; it is `nil' if Emacs can be
     certain that this is not so.