Venus::Process

Process Class

Process Class for Perl 5

method: async method: await method: chdir method: check method: count method: daemon method: data method: decode method: disengage method: encode method: engage method: exchange method: exit method: followers method: fork method: forks method: future method: is_dyadic method: is_follower method: is_leader method: is_registered method: is_unregistered method: join method: kill method: killall method: leader method: leave method: limit method: new method: others method: others_active method: others_inactive method: poll method: pool method: pid method: pids method: ping method: ppid method: prune method: recall method: recallall method: recv method: recvall method: register method: registrants method: restart method: send method: sendall method: serve method: setsid method: started method: status method: stderr method: stdin method: stdout method: stopped method: sync method: trap method: wait method: waitall method: watch method: watchlist method: work method: works method: unregister method: untrap method: unwatch

package main;

use Venus::Process;

my $parent = Venus::Process->new;

my $process = $parent->fork;

if ($process) {
  # do something in child process ...
  $process->exit;
}
else {
  # do something in parent process ...
  $parent->wait(-1);
}

# $parent->exit;

This package provides methods for handling and forking processes.

Venus::Kind::Utility

Venus::Role::Accessible Venus::Role::Buildable Venus::Role::Explainable Venus::Role::Valuable

The alarm attribute is used in calls to alarm when the process is forked, installing an alarm in the forked process if set.

alarm(number $seconds) (number)

{ since => '2.40', }

=example-1 alarm

# given: synopsis

package main;

my $alarm = $parent->alarm;

# undef

The async method creates a new Venus::Process object and asynchronously runs the callback provided via the "work" method. Both process objects are configured to be are dyadic, i.e. representing an exclusing bi-directoral relationship. Additionally, the callback return value will be automatically made available via the "await" method unless it's undefined. This method returns the newly created "dyadic" process object.

async(coderef $code, any @args) (Venus::Process)

{ since => '3.40', }

The await method expects to operate on a "dyadic" process object and blocks the execution of the current process until a value is received from its couterpart. If a timeout is provided, execution will be blocked until a value is received or the wait time expires. If a timeout of 0 is provided, execution will not be blocked. If no timeout is provided at all, execution will block indefinitely.

await(number $timeout) (arrayref)

{ since => '3.40', }

The chdir method changes the working directory the current process is operating within.

chdir(string $path) (Venus::Process)

{ since => '0.06', }

=example-1 chdir

# given: synopsis;

$parent = $parent->chdir;

# bless({...}, 'Venus::Process')

The check method does a non-blocking "waitpid" in perlfunc operation and returns the wait status. In list context, returns the specified process' exit code (if terminated).

check(number $pid) (number, number)

{ since => '0.06', }

=example-1 check

package main;

use Venus::Process;

my $parent = Venus::Process->new;

my ($process, $pid) = $parent->fork;

if ($process) {
  # in forked process ...
  $process->exit;
}

my $check = $parent->check($pid);

# 0

The count method dispatches to the method specified (or the "watchlist" if not specified) and returns a count of the items returned from the dispatched call.

count(string | coderef $code, any @args) (number)

{ since => '2.40', }

The daemon method detaches the process from controlling terminal and runs it in the background as system daemon. This method internally calls "disengage" and "setsid" and attempts to change the working directory to the root directory.

daemon() (Venus::Process)

{ since => '0.06', }

=example-1 daemon

# given: synopsis;

my $daemon = $parent->daemon; # exits parent immediately

# in forked process ...

# $daemon->exit;

The data method returns the number of messages sent to the current process, from the PID or PIDs provided (if any). If no PID list is provided, the count returned is based on the PIDs returned from "watchlist".

data(number @pids) (number)

{ since => '2.91', }

The decode method accepts a string representation of a Perl value and returns the Perl value.

decode(string $data) (any)

{ since => '2.91', }

The disengage method limits the interactivity of the process by changing the working directory to the root directory and redirecting its standard file descriptors from and to /dev/null, or the OS' equivalent. These state changes can be undone by calling the "engage" method.

disengage() (Venus::Process)

{ since => '0.06', }

=example-1 disengage

# given: synopsis;

$parent = $parent->disengage;

# bless({...}, 'Venus::Process')

The encode method accepts a Perl value and returns a string representation of that Perl value.

encode(any $data) (string)

{ since => '2.91', }

The engage method ensures the interactivity of the process by changing the working directory to the directory used to launch the process, and by redirecting/returning its standard file descriptors from and to their defaults. This method effectively does the opposite of the "disengage" method.

engage() (Venus::Process)

{ since => '0.06', }

=example-1 engage

# given: synopsis;

$parent = $parent->engage;

# bless({...}, 'Venus::Process')

The exchange method gets and/or sets the name of the data exchange. The exchange is the ontext in which processes can register and cooperate. Process can cooperate in different exchanges (or contexts) and messages sent to a process in one context are not available to be retrieved will operating in another exchange (or context).

exchange(string $name) (any)

{ since => '2.91', }

The exit method exits the program immediately.

exit(number $status) (number)

{ since => '0.06', }

=example-1 exit

# given: synopsis;

my $exit = $parent->exit;

# 0

The followers method returns the list of PIDs registered under the current "exchange" who are not the "leader".

followers() (arrayref)

{ since => '2.91', }

The fork method calls the system "fork" in perlfunc function and creates a new process running the same program at the same point (or call site). This method returns a new Venus::Process object representing the child process (from within the execution of the child process (or fork)), and returns undef to the parent (or originating) process. In list context, this method returns both the process and PID (or process ID) of the child process. If a callback or argument is provided it will be executed in the child process.

fork(string | coderef $code, any @args) (Venus::Process, number)

{ since => '0.06', }

=example-1 fork

# given: synopsis;

$process = $parent->fork;

# if ($process) {
#   # in forked process ...
#   $process->exit;
# }
# else {
#   # in parent process ...
#   $parent->wait(-1);
# }

# in child process

# bless({...}, 'Venus::Process')

The forks method creates multiple forks by calling the "fork" method n times, based on the count specified. As with the "fork" method, this method returns a new Venus::Process object representing the child process (from within the execution of the child process (or fork)), and returns undef to the parent (or originating) process. In list context, this method returns both the process and an arrayref of PID values (or process IDs) for each of the child processes created. If a callback or argument is provided it will be executed in each child process.

forks(string | coderef $code, any @args) (Venus::Process, within[arrayref, number])

{ since => '0.06', }

=example-1 forks

# given: synopsis;

$process = $parent->forks(5);

# if ($process) {
#   # do something in (each) forked process ...
#   $process->exit;
# }
# else {
#   # do something in parent process ...
#   $parent->wait(-1);
# }

# bless({...}, 'Venus::Process')

The future method creates a new object via "async" which runs the callback asynchronously and returns a Venus::Future object with a promise which eventually resolves to the value emitted or error raised.

future(coderef $code, any @args) (Venus::Future)

{ since => '3.55', }

The is_dyadic method returns true is the process is configured to exclusively communicate with one other process, otherwise returns false.

is_dyadic() (boolean)

{ since => '3.40', }

The is_follower method returns true if the process is not the "leader", otherwise returns false.

is_follower() (boolean)

{ since => '2.91', }

The is_leader method returns true if the process is the "leader", otherwise returns false.

is_leader() (boolean)

{ since => '2.91', }

The is_registered method returns true if the process has registered using the "register" method, otherwise returns false.

is_registered() (boolean)

{ since => '2.91', }

The is_unregistered method returns true if the process has unregistered using the "unregister" method, or had never registered at all, otherwise returns false.

is_unregistered() (boolean)

{ since => '2.91', }

The join method sets the "exchange", registers the process with the exchange using "register", and clears the "watchlist", then returns the invocant.

join(string $name) (Venus::Process)

{ since => '2.91', }

The kill method calls the system "kill" in perlfunc function which sends a signal to a list of processes and returns truthy or falsy. Note: A truthy result doesn't necessarily mean all processes were successfully signalled.

kill(string $signal, number @pids) (number)

{ since => '0.06', }

=example-1 kill

# given: synopsis;

if ($process = $parent->fork) {
  # in forked process ...
  $process->exit;
}

my $kill = $parent->kill('term', int $process);

# 1

The killall method accepts a list of PIDs (or uses the "watchlist" if not provided) and returns the result of calling the "kill" method for each PID. Returns a list in list context.

killall(string $name, number @pids) (arrayref)

{ since => '2.40', }

The leader method uses a simple leader election algorithm to determine the process leader and returns the PID for that process. The leader is always the lowest value active PID (i.e. that responds to "ping").

leader() (number)

{ since => '2.91', }

The leave method sets the "exchange" to undefined, unregisters the process using "unregister", and clears the "watchlist", then returns the invocant.

leave(string $name) (Venus::Process)

{ since => '2.91', }

The limit method blocks the execution of the current process until the number of processes in the "watchlist" falls bellow the count specified. The method returns true once execution continues if execution was blocked, and false if the limit has yet to be reached.

limit(number $count) (boolean)

{ since => '3.40', }

The new method constructs an instance of the package.

new(any @args) (Venus::Process)

{ since => '4.15', }

The others method returns all "registrants" other than the current process, i.e. all other registered process PIDs whether active or inactive.

others() (arrayref)

{ since => '2.91', }

The others_active method returns all "registrants" other than the current process which are active, i.e. all other registered process PIDs that responds to "ping".

others_active() (arrayref)

{ since => '2.91', }

The others_inactive method returns all "registrants" other than the current process which are inactive, i.e. all other registered process PIDs that do not respond to "ping".

others_inactive() (arrayref)

{ since => '2.91', }

The poll method continuously calls the named method or coderef and returns the result that's not undefined, or throws an exception on timeout. If no method name is provided this method will default to calling "recvall".

poll(number $timeout, string | coderef $code, any @args) (arrayref)

{ since => '2.91', }

The pool method blocks the execution of the current process until the number of "other" processes are registered and pingable. This method returns the invocant when successful, or throws an exception if the operation timed out.

pool(number $count, number $timeout) (Venus::Process)

{ since => '2.91', }

The pid method returns the PID of the current process.

pid() (number)

{ since => '2.40', }

The pids method returns the PID of the current process, and the PIDs of any child processes.

pids() (arrayref)

{ since => '2.40', }

The ping method returns truthy if the process of the PID provided is active. If multiple PIDs are provided, this method will return the count of active PIDs.

ping(number @pids) (number)

{ since => '2.01', }

=example-1 ping

# given: synopsis;

if ($process = $parent->fork) {
  # in forked process ...
  $process->exit;
}

my $ping = $parent->ping(int $process);

# 1

The ppid method returns the PID of the parent process (i.e. the process which forked the current process, if any).

ppid() (number)

{ since => '2.91', }

The prune method removes all stopped processes and returns the invocant.

prune() (Venus::Process)

{ since => '2.40', }

The recall method returns the earliest message, sent by the current process to the process specified by the PID provided, which is no longer active (i.e. responding to "ping").

recall(number $pid) (any)

{ since => '2.91', }

The recallall method performs a "recall" on the parent process (if any) via "ppid" and any process listed in the "watchlist", and returns the results.

recallall() (arrayref)

{ since => '2.91', }

The recv method returns the earliest message found from the process specified by the PID provided.

recv(number $pid) (any)

{ since => '2.91', }

The recvall method performs a "recv" on the parent process (if any) via "ppid" and any process listed in the "watchlist", and returns the results.

recvall() (arrayref)

{ since => '2.91', }

The register method declares that the process is willing to cooperate with others (e.g. "send" nad "recv" messages), in a way that's discoverable by other processes, and returns the invocant.

register() (Venus::Process)

{ since => '2.91', }

The registrants method returns the PIDs for all the processes that registered using the "register" method whether they're currently active or not.

registrants() (arrayref)

{ since => '2.91', }

The restart method executes the callback provided for each PID returned by the "stopped" method, passing the pid and the results of "check" to the callback as arguments, and returns the result of each call as an arrayref. In list context, this method returns a list.

restart(coderef $callback) (arrayref)

{ since => '2.40', }

The send method makes the data provided available to the process specified by the PID provided.

send(number $pid, any $data) (Venus::Process)

{ since => '2.91', }

The sendall method performs a "send" on the parent process (if any) via "ppid" and any process listed in the "watchlist", and returns the invocant.

sendall(any $data) (Venus::Process)

{ since => '2.91', }

The serve method executes the callback using "work" until "limit" blocks the execution of the current process, indefinitely. It has the effect of serving the callback and maintaining the desired number of forks until killed or gracefully shutdown.

serve(number $count, coderef $callback) (Venus::Process)

{ since => '3.40', }

The setsid method calls the "setsid" in POSIX function and sets the process group identifier of the current process.

setsid() (number)

{ since => '0.06', }

=example-1 setsid

# given: synopsis;

my $setsid = $parent->setsid;

# 1

The started method returns a list of PIDs whose processes have been started and which have not terminated. Returns a list in list context.

started() (arrayref)

{ since => '2.40', }

The status method executes the callback provided for each PID in the "watchlist", passing the pid and the results of "check" to the callback as arguments, and returns the result of each call as an arrayref. In list context, this method returns a list.

status(coderef $callback) (arrayref)

{ since => '2.40', }

The stderr method redirects STDERR to the path provided, typically /dev/null or some equivalent. If called with no arguments STDERR will be restored to its default.

stderr(string $path) (Venus::Process)

{ since => '0.06', }

=example-1 stderr

# given: synopsis;

$parent = $parent->stderr;

# bless({...}, 'Venus::Process')

The stdin method redirects STDIN to the path provided, typically /dev/null or some equivalent. If called with no arguments STDIN will be restored to its default.

stdin(string $path) (Venus::Process)

{ since => '0.06', }

=example-1 stdin

# given: synopsis;

$parent = $parent->stdin;

# bless({...}, 'Venus::Process')

The stdout method redirects STDOUT to the path provided, typically /dev/null or some equivalent. If called with no arguments STDOUT will be restored to its default.

stdout(string $path) (Venus::Process)

{ since => '0.06', }

=example-1 stdout

# given: synopsis;

$parent = $parent->stdout;

# bless({...}, 'Venus::Process')

The stopped method returns a list of PIDs whose processes have terminated. Returns a list in list context.

stopped() (arrayref)

{ since => '2.40', }

The sync method blocks the execution of the current process until the number of "other" processes are registered, pingable, and have each sent at-least one message to the current process. This method returns the invocant when successful, or throws an exception if the operation timed out.

sync(number $count, number $timeout) (Venus::Process)

{ since => '2.91', }

The trap method registers a process signal trap (or callback) which will be invoked whenever the current process receives that matching signal. The signal traps are globally installed and will overwrite any preexisting behavior. Signal traps are inherited by child processes (or forks) but can be overwritten using this method, or reverted to the default behavior by using the "untrap" method.

trap(string $name, string | coderef $expr) (Venus::Process)

{ since => '0.06', }

=example-1 trap

# given: synopsis;

$parent = $parent->trap(term => sub{
  die 'Something failed!';
});

# bless({...}, 'Venus::Process')

The wait method does a blocking "waitpid" in perlfunc operation and returns the wait status. In list context, returns the specified process' exit code (if terminated).

wait(number $pid) (number, number)

{ since => '0.06', }

=example-1 wait

package main;

use Venus::Process;

my $parent = Venus::Process->new;

my ($process, $pid) = $parent->fork;

if ($process) {
  # in forked process ...
  $process->exit;
}

my $wait = $parent->wait($pid);

# 0

The waitall method does a blocking "wait" call for all processes based on the PIDs provided (or the PIDs returned by "watchlist" if not provided) and returns an arrayref of results from calling "wait" on each PID. Returns a list in list context.

waitall(number @pids) (arrayref)

{ since => '2.40', }

The watch method records PIDs to be watched, e.g. using the "status" method and returns all PIDs being watched. Returns a list in list context.

watch(number @pids) (arrayref)

{ since => '2.40', }

The watchlist method returns the recorded PIDs. Returns a list in list context.

watchlist() (arrayref)

{ since => '2.40', }

The work method forks the current process, runs the callback provided in the child process, and immediately exits after. This method returns the PID of the child process. It is recommended to install an "alarm" in perlfunc in the child process (i.e. callback) to avoid creating zombie processes in situations where the parent process might exit before the child process is done working.

work(string | coderef $code, any @args) (number)

{ since => '0.06', }

=example-1 work

# given: synopsis;

my $pid = $parent->work(sub{
  my ($process) = @_;
  # in forked process ...
  $process->exit;
});

# $pid

The works method creates multiple forks by calling the "work" method n times, based on the count specified. The works method runs the callback provided in the child process, and immediately exits after with an exit code of 0 by default. This method returns the PIDs of the child processes. It is recommended to install an "alarm" in perlfunc in the child process (i.e. callback) to avoid creating zombie processes in situations where the parent process might exit before the child process is done working.

works(number $count, coderef $callback, any @args) (arrayref)

{ since => '2.40', }

The unregister method declares that the process is no longer willing to cooperate with others (e.g. "send" nad "recv" messages), and will no longer be discoverable by other processes, and returns the invocant.

unregister() (Venus::Process)

{ since => '2.91', }

The untrap method restores the process signal trap specified to its default behavior. If called with no arguments, it restores all signal traps overwriting any user-defined signal traps in the current process.

untrap(string $name) (Venus::Process)

{ since => '0.06', }

=example-1 untrap

# given: synopsis;

$parent->trap(chld => 'ignore')->trap(term => sub{
  die 'Something failed!';
});

$parent = $parent->untrap('term');

# bless({...}, 'Venus::Process')

The unwatch method removes the PIDs provided from the watchlist and returns the list of PIDs remaining to be watched. In list context returns a list.

unwatch(number @pids) (arrayref)

{ since => '2.40', }

# given: synopsis;

$parent->chdir('/path/to/nowhere');

# Error! (on.chdir)

# given: synopsis;

$parent->stderr('/path/to/nowhere');

# Error! (on.stderr)

# given: synopsis;

$parent->stdin('/path/to/nowhere');

# Error! (on.stdin)

# given: synopsis;

$parent->stdout('/path/to/nowhere');

# Error! (on.stdout)

This package overloads the "" operator.

This package overloads the ~~ operator.

t/Venus.t: present: authors t/Venus.t: present: license

cpanm Venus

perl -MCPAN -e shell
install Venus