PLMD::Subprocess Class Reference

Class managing a subprocess. More...

#include <Subprocess.h>

Classes
class	Handler
	Class used to cont/stop a Subprocess in an exception safe manner. More...

Public Member Functions
	Subprocess (const std::string &cmd)
	Constructor with a command line.
	~Subprocess ()
	Destructor.
void	cont () noexcept
	Send a SIGCONT to the subprocess.
Handler	contStop () noexcept
	Returns a handler to temporarily resume the process.
void	flush ()
	Flush communication to process.
Subprocess &	getline (std::string &)
	Get a line from the subprocess.
void	stop () noexcept
	Send a SIGSTOP to the subprocess.

Static Public Member Functions
static bool	available () noexcept
	Check if subprocess facilities are available.

Private Attributes
IFile	child_to_parent
	PLUMED file object, child to parent.
int	fcp =0
	File descriptor, child to parent.
int	fpc =0
	File descriptor, parent to child.
FILE *	fpcp =NULL
	File pointer, child to parent.
FILE *	fppc =NULL
	File pointer, parent to child.
OFile	parent_to_child
	PLUMED file object, parent to child.
std::unique_ptr< SubprocessPid >	pid
	Process ID.

Friends
template<class T>
Subprocess &	operator<< (Subprocess &ep, const T &t)
	Write something to the subprocess.

Detailed Description

Class managing a subprocess.

The subprocess is launched and one can interact with it through a pipe.

In order not to consume resources, it might be possible to use this syntax:

// at construction:
Subprocess sp;
sp.stop();

// when needed
{
  auto h=sp.contStop();
  sp<<"command\n";
  sp.flush();
  sp.getline(answer);
}
// when h goes out of scope, subprocess is stopped again.
// If an exception is raised in the block, the subprocess is stopped as well.

Warning

Currently stop and cont are giving problems with some MPI implementation, In addition, notice that the stop signal is only sent to the child process and not to the subsequently spawn processes, so it might not work as intended. This feature is left here but is probably no a good idea to use it. It can be enabled with export PLUMED_ENABLE_SIGNALS=1.

Constructor & Destructor Documentation

Subprocess()

PLMD::Subprocess::Subprocess ( const std::string & cmd )

explicit

Constructor with a command line.

~Subprocess()

PLMD::Subprocess::~Subprocess

(

)

Destructor.

Member Function Documentation

available()

bool PLMD::Subprocess::available ( )

staticnoexcept

Check if subprocess facilities are available.

If it returns false, any call to Subprocess constructor will raise an exception.

cont()

void PLMD::Subprocess::cont ( )

noexcept

Send a SIGCONT to the subprocess.

Better used through contStop() method.

contStop()

Handler PLMD::Subprocess::contStop ( )

inlinenoexcept

Returns a handler to temporarily resume the process.

flush()

void PLMD::Subprocess::flush

(

)

Flush communication to process.

getline()

Subprocess & PLMD::Subprocess::getline

(

std::string &

line

)

Get a line from the subprocess.

stop()

void PLMD::Subprocess::stop ( )

noexcept

Send a SIGSTOP to the subprocess.

Better used through contStop() method.

Friends And Related Symbol Documentation

operator<<

template<class T>

Subprocess & operator<< ( Subprocess & ep, const T & t )

friend

Write something to the subprocess.

Member Data Documentation

child_to_parent

IFile PLMD::Subprocess::child_to_parent

private

PLUMED file object, child to parent.

Used to simplify formatting

fcp

int PLMD::Subprocess::fcp =0

private

File descriptor, child to parent.

fpc

int PLMD::Subprocess::fpc =0

private

File descriptor, parent to child.

fpcp

FILE* PLMD::Subprocess::fpcp =NULL

private

File pointer, child to parent.

fppc

FILE* PLMD::Subprocess::fppc =NULL

private

File pointer, parent to child.

parent_to_child

OFile PLMD::Subprocess::parent_to_child

private

PLUMED file object, parent to child.

Used to simplify formatting

pid

std::unique_ptr<SubprocessPid> PLMD::Subprocess::pid

private

Process ID.

We store this rather than pid_t to avoid including <unistd.h> in this header file. This remains nullptr in the child process.

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The documentation for this class was generated from the following files:

• tools/Subprocess.h
• tools/Subprocess.cpp