Processes
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In the terminology of operating systems, a "process" is a space in
which a program can execute. Emacs runs in a process. Emacs Lisp
programs can invoke other programs in processes of their own. These are
called "subprocesses" or "child processes" of the Emacs process, which
is their "parent process".
A subprocess of Emacs may be "synchronous" or "asynchronous",
depending on how it is created. When you create a synchronous
subprocess, the Lisp program waits for the subprocess to terminate
before continuing execution. When you create an asynchronous
subprocess, it can run in parallel with the Lisp program. This kind of
subprocess is represented within Emacs by a Lisp object which is also
called a "process". Lisp programs can use this object to communicate
with the subprocess or to control it. For example, you can send
signals, obtain status information, receive output from the process, or
send input to it.
- Function: processp object
This function returns `t' if OBJECT is a process, `nil' otherwise.