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(librep.info)Process Objects

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Process Objects
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   A "process object" is a type of Lisp object used to provide a link
between a `physical' process running in the operating system and the
Lisp system. Each process object consists of a number of values
(references to other Lisp objects); these values are used when the
object is used to run a subprocess.

   Process objects which aren't currently being used to run a subprocess
store the exit value of the last subprocess which was run on that
object.

 - Function: processp object
     This function returns true when its argument is a process object.

   The programmer-accessible components of a process object are,

"Output stream"
     A normal Lisp output stream (Note: Output Streams), all data
     which the subprocess outputs to its `stdout' channel is copied to
     this output stream. Note: Process I/O.

"Error stream"
     A normal Lisp output stream (Note: Output Streams), all data
     which the subprocess outputs to its `stderr' channel is copied to
     this output stream. Unless explicitly specified error output goes
     to the `stdout' stream. Note: Process I/O.

"State change function"
     A Lisp function, called each time the state of the subprocess
     being run on the object changes. Note: Process States.

"Program name"
     The name of the program (a string) to execute when the subprocess
     is created.

"Program arguments"
     A list of strings defining the arguments which the program executed
     is given.

"Directory"
     When a subprocess is started its current working directory is set
     to the directory named by this component of its process object.

"Connection type"
     Asynchronous subprocesses (Note: Asynchronous Processes) use this
     component to decide how to connect to the I/O channels of the
     subprocess.  Current options include pseudo-terminals and pipes.

 - Function: make-process #!optional output-stream state-function
          directory program args
     This functions creates and returns a new process object. _No
     subprocess will be started._

     The optional arguments are used to define the values of the
     components of the new process object, any undefined components
     will be set to default or null values.

   For each component of a process object two functions exist; one to
read the component's value in a specific process object, the other to
set the component's value.

 - Function: process-prog process
     Returns the value of the program name component of the process
     object PROCESS.

 - Function: set-process-prog process prog-name
     Sets the value of the program name component of the process object
     PROCESS to the string PROG-NAME, then returns PROG-NAME.

 - Function: process-args process
     Returns the value of the program arguments component of the
     process object PROCESS.

 - Function: set-process-args process arg-list
     Sets the value of the program arguments component of the process
     object PROCESS to the list ARG-LIST, then returns ARG-LIST.

 - Function: process-dir process
     Returns the value of the directory component of the process object
     PROCESS.

 - Function: set-process-dir process directory
     Sets the value of the directory component of the process object
     PROCESS to the string DIRECTORY, then returns DIRECTORY.

 - Variable: process-environment
     This is a list of environment variable definitions, as well as
     being used by the `setenv' and `getenv' functions (Note:
     Environment Variables), it also provides the environment of all
     started subprocesses.

          (car process-environment)
              => "LOGNAME=john"

 - Function: active-processes
     Returns a list containing all active (i.e. running or stopped)
     process objects.