Venus::Process

Process Class

Process Class for Perl 5

method: chdir method: check method: daemon method: disengage method: engage method: exit method: fork method: forks method: kill method: ping method: setsid method: stderr method: stdin method: stdout method: trap method: wait method: work method: untrap

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

chdir(Str $path) (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(Int $pid) (Int, Int)

{ 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 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() (Process)

{ since => '0.06', }

=example-1 daemon

# given: synopsis;

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

# in forked process ...

# $daemon->exit;

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() (Process)

{ since => '0.06', }

=example-1 disengage

# given: synopsis;

$parent = $parent->disengage;

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

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() (Process)

{ since => '0.06', }

=example-1 engage

# given: synopsis;

$parent = $parent->engage;

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

The exit method exits the program immediately.

exit(Int $status) (Int)

{ since => '0.06', }

=example-1 exit

# given: synopsis;

my $exit = $parent->exit;

# 0

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(Str | CodeRef $code, Any @args) (Process, Int)

{ 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(Str | CodeRef $code, Any @args) (Process, ArrayRef[Int])

{ 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 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(Str $signal, Int @pids) (Int)

{ 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 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(Int @pids) (Int)

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

setsid() (Int)

{ since => '0.06', }

=example-1 setsid

# given: synopsis;

my $setsid = $parent->setsid;

# 1

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(Str $path) (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(Str $path) (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(Str $path) (Process)

{ since => '0.06', }

=example-1 stdout

# given: synopsis;

$parent = $parent->stdout;

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

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(Str $name, Str | CodeRef $expr) (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(Int $pid) (Int, Int)

{ 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 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(Str | CodeRef $code, Any @args) (Int)

{ since => '0.06', }

=example-1 work

# given: synopsis;

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

# $pid

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(Str $name) (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')

This package overloads the "" operator.

This package overloads the ~~ operator.

t/Venus.t: pdml: authors t/Venus.t: pdml: license

cpanm Venus

perl -MCPAN -e shell
install Venus