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 (see Process Information). Otherwise, the coding system comes from
coding-system-for-write, if that is non-
nil; or else from the defaulting mechanism (see 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 (including the one currently running), 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
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")
function process-send-region process start end
This function sends the text in the region defined by
end as standard input to
An error is signaled unless both
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
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.