add documentation

src/lib/process.pl

@@ -10,6 +10,37 @@
 :- use_module(library(iso_ext)).
 :- use_module(library(lists), [append/3, member/2, maplist/2, maplist/3, select/3]).
 
+
+%% process_create(+Exe, +Args:list, +Options).
+%
+% Create a new process by executing the executable Exe and passing it the Arguments Args.
+%
+% Note: On windows please take note of [windows argument splitting](https://doc.rust-lang.org/std/process/index.html#windows-argument-splitting).
+% 
+% Options is a list consisting of the following options:
+%
+%  * `cwd(+Path)`           Set the processes working directory to `Path`
+%  * `process(-Pid)`        `Pid` will be assigned the spawned processes process id
+%  * `env(+List)`           Don't inherit environment variables and set the variables defined in `List`
+%  * `environment(+List)`   Inherit environment variables and set/override the variables defined in `List`
+%  * `stdin(Spec)`, `stdout(Spec)` or `stderr(Spec)` defines how to redirect the spawned processes io streams
+%
+%  The elements of `List` in `env(List)`/`environment(List)` List must be string pairs using `=/2`.
+%  `env/1` and `environment/1` may not be both specified.
+%
+%  The following stdio `Spec` are available:
+%  
+%  * `std`          inherit the current processes original stdio streams (does currently not account for stdio being changed by `set_input` or `set_output`)
+%  * `file(+Path)`  attach the strea to the file at `Path`
+%  * `null`         discards writes and behaves as eof for read. Equivalent to using `file(/dev/null)`
+%  * `pipe(-Steam)` create a new pipe and assigne one end to the created process and the other end to `Stream`
+%
+% Specifying an option multiple times is an error, when an option is not specified the following defaults apply:
+%
+% - `cwd(".")`
+% - `environment([])`
+% - `stdin(std)`, `stdout(std)`, `stderr(std)`
+%
 process_create(Exe, Args, Options) :- 
     must_be(chars, Exe),
     must_be(list, Args),
@@ -33,8 +64,32 @@ process_create(Exe, Args, Options) :-
     simplify_env(Env, Env1),
     '$process_create'(Exe, Args, Stdin1, Stdout1, Stderr1, Env1, Cwd, Pid).
 
+
+%% process_wait(+Pid, Status).
+%
+% See `process_create/3` with `Options = []`
+%
 process_wait(Pid, Status) :- process_wait(Pid, Status, []).
 
+
+%% process_wait(+Pid, Status, Options).
+%
+% Wait for the child process with `Pid` to exit.
+%
+% Only works for processes spawned with `process_create/3` that have not yet been release with `process_release/1`
+%
+% When the process exits regulary `Status` will be unified with `exit(Exit)` where `Exit` is the processes exit code.
+% When the process exits was killed `Status` will be unified with `killed(Signal)` where `Signal` is the signal number that killed the process.
+% When the process doesn't exit before the timeout `Status` will be unified with `timeout`.
+%
+% `Options` is a a list of the following options
+%
+%  * timeout(Timeout) supported values for `Timeout` are 0 or `infinite`
+%
+% Each options may be specified at most once, when an option is not specified the following defaults apply:
+%
+% - timeout(infinite)
+%
 process_wait(Pid, Status, Options) :- 
     must_be(integer, Pid),
     must_be_known_options([timeout], [], Options),check_options(
@@ -49,10 +104,26 @@ process_wait(Pid, Status, Options) :-
 valid_timeout(timeout(infinite)).
 valid_timeout(timeout(0)).
 
+
+%% process_kill(+Pid).
+%
+% Kill the child process identified by `Pid`.
+% On Unix this sends SIGKILL.
+%
+% Only works for processes spawned with `process_create/3` that have not yet been release with `process_release/1`
+% 
 process_kill(Pid) :- 
     must_be(integer, Pid),
     '$process_kill'(Pid).
 
+%% process_release(+Pid)
+%
+% release child process object of the process identified by `Pid`
+%
+% It's an error if 
+% * the `Pid` is not associated with a child process created by `process_create/3`,
+% * the child project object has already been released 
+%
 process_release(Pid) :- 
     process_wait(Pid, _),
     '$process_release'(Pid).