process

Process, System-V, and POSIX libraries wrapper module. More...

Files
file	process.h
	Process, System-V, and POSIX libraries wrapper module.

Process handling
pid_t	pfork (void)
	fork wrapper function. More...
pid_t	pwait (int *status)
	wait wrapper function. More...
pid_t	pwaitpid (pid_t pid, int *status, int options)
	waitpid wrapper function. More...
void	pkill (pid_t pid, int sig)
	kill wrapper function. More...
void	pexecl (const char *pathname, const char *arg,...)
	execl wrapper function. More...
void	psigaction (int signum, const struct sigaction *act, struct sigaction *oldact)
	sigaction wrapper function. More...

System V - shared memory
Example #include <process.h> // #include <sys/shm.h> ... int shmid; // creation: shmid = pshmget(key, size, 0600 | IPC_CREAT | IPC_EXCL); // or, use existing: shmid = pshmget(key, 0, 0); ... // attach shm to pointer address: void* p = pshmat(shmid, NULL, 0); ... // detach shm from pointer address: pshmdt(p); ... // destroy shm: pshmctl(shmid, IPC_RMID, NULL);
int	pshmget (key_t key, size_t size, int shmflg)
	shmget wrapper function. More...
int	pshmctl (int shmid, int cmd, struct shmid_ds *buf)
	shmctl wrapper function. More...
void *	pshmat (int shmid, const void *shmaddr, int shmflg)
	shmat wrapper function. More...
void	pshmdt (const void *shmaddr)
	shmdt wrapper function. More...

System V - semaphores
Example #include <process.h> // #include <sys/sem.h> ... int semid; // creation: semid = psemget(key, 1, 0600 | IPC_CREAT | IPC_EXCL); // 1 semaphore! // or, use existing: semid = psemget(key, 0, 0); ... // decrement: struct sembuf down = {0, -1, 0}; psemop(semid, &down, 1); // or, simply use provided function: psem_down(semid, 0); // NOTE: there is no sem_down in default library! ... // increment: struct sembuf up = {0, 1, 0}; psemop(semid, &up, 1); // or, simply use provided function: psem_up(semid, 0); // NOTE: there is no sem_up in default library! ... // destroy sem 0: psemctl(semid, 0, IPC_RMID, NULL);
int	psemget (key_t key, int nsems, int semflg)
	semget wrapper function. More...
int	psemctl (int semid, int semnum, int cmd)
	semctl wrapper function. More...
int	psemctl (int semid, int semnum, int cmd, void *u)
void	psemop (int semid, struct sembuf *sops, size_t nsops)
	semop wrapper function. More...
void	psem_up (int semid, short unsigned int index)
	Increment a semaphore (uses psemop()).
void	psem_down (int semid, short unsigned int index)
	Decrements a semaphore (uses psemop()).
void	psem_down2 (int semid, short unsigned int index1, unsigned int index2)
	Decrements atomically two semaphores in a System V semaphore array (uses psemop()).

System V - message queues
Example #include <process.h> // #include <sys/msg.h> ... typedef struct Item { ... } Item; typedef struct Message { long type; Item item; } Message; ... int msgid; // creation: msgid = pmsgget(key, 0600 | IPC_CREAT | IPC_EXCL); // or, use existing: msgid = pmsgget(key, 0); ... Message msg; // send msg: msg = ...; pmsgsnd(msgid, &msg, sizeof(Item), 0); ... // receive msg: pmsgrcv(msgid, &msg, sizeof(Item), type, 0); ... // destroy msg: pmsgctl(msgid, IPC_RMID, NULL);
int	pmsgget (key_t key, int msgflg)
	msgget wrapper function. More...
int	pmsgctl (int msqid, int cmd, struct msqid_ds *buf)
	msgctl wrapper function. More...
void	pmsgsnd (int msqid, const void *msgp, size_t msgsz, int msgflg)
	msgsnd wrapper function. More...
size_t	pmsgrcv (int msqid, void *msgp, size_t msgsz, long msgtyp, int msgflg)
	msgrcv wrapper function. More...

POSIX semaphores
sem_t *	psem_open (const char *name, int oflag)
	sem_open wrapper function. More...
sem_t *	psem_open (const char *name, int oflag, mode_t mode, unsigned int value)
void	psem_close (sem_t *sem)
	sem_close wrapper function. More...
void	psem_unlink (const char *name)
	sem_unlink wrapper function. More...
void	psem_init (sem_t *sem, int pshared, unsigned int value)
	sem_init wrapper function. More...
void	psem_destroy (sem_t *sem)
	sem_destroy wrapper function. More...
void	psem_wait (sem_t *sem)
	sem_wait wrapper function. More...
int	psem_trywait (sem_t *sem)
	sem_trywait wrapper function. More...
int	psem_timedwait (sem_t *sem, const struct timespec *abs_timeout)
	sem_timedwait wrapper function. More...
void	psem_post (sem_t *sem)
	sem_post wrapper function. More...

UNIX pipes
void	ppipe (int pipefd[2])
	pipe wrapper function. More...
FILE *	ppopen (const char *command, const char *type)
	popen wrapper function. More...
void	ppclose (FILE *stream)
	pclose wrapper function. More...

Detailed Description

Process, System-V, and POSIX libraries wrapper module.

This module removes defensive programming approach of native libraries.

All implemented functions, have exactly the same arguments and/or result of the original function, with the exception of returning an error indication.

Errors are handled by the implementation of two policies:

1. EXIT_POLICY (default): describes the failed call in stderr (with the identification of the errno error, and the precise location the call), generates a segmentation fault (enabling a stack trace within a debugger like gdb), and exits program execution;
2. EXCEPTION_POLICY: throws a int exception with the (errno) status error returned by the original function.

System V group of IPC mechanisms

There are three resources for IPC: shared memory, semaphores, and message queues.

Common to all, is resource handling through a non-negative integer identifier. After proper creation and initialization, different processes can establish communication using the same integer identifier.

A key (key_t) is used to establish this common identifier. There are three possibilities to define a key:

1. IPC_PRIVATE: In this case an alternative channel to communicate the identifier between processes is necessary (parent/child fork, file system, ...).
2. A fixed predetermined key number (may collide with other existing keys).
3. ftok function to generate a key from a path and a byte integer.

Usage:

• create new identifier: msgget/semget/shmget with a key and IPC_CREAT and IPC_EXCL flags
• get existing identifier: msgget/semget/shmget with a key and other arguments as zero

Author

Miguel Oliveira e Silva, 2017-2018

Function Documentation

pfork()

pid_t pfork

(

void

)

fork wrapper function.

Other documentation in

man 2 fork 

See also

https://man.cx/fork(2)

pwait()

pid_t pwait

(

int *

status

)

wait wrapper function.

Other documentation in

man 2 wait 

See also

https://man.cx/wait(2)

pwaitpid()

pid_t pwaitpid	(	pid_t	pid,
		int *	status,
		int	options
	)

waitpid wrapper function.

Other documentation in

man 2 waitpid 

See also

https://man.cx/waitpid(2)

pkill()

void pkill	(	pid_t	pid,
		int	sig
	)

kill wrapper function.

Other documentation in

man 2 kill 

See also

https://man.cx/kill(2)

pexecl()

void pexecl	(	const char *	pathname,
		const char *	arg,
			...
	)

execl wrapper function.

Other documentation in

man 3 execl 

See also

https://man.cx/execl(3)

psigaction()

void psigaction	(	int	signum,
		const struct sigaction *	act,
		struct sigaction *	oldact
	)

sigaction wrapper function.

Other documentation in

man 2 sigaction 

See also

https://man.cx/sigaction(2)

pshmget()

int pshmget	(	key_t	key,
		size_t	size,
		int	shmflg
	)

shmget wrapper function.

Precondition:

(size > 0) || !(shmflg & IPC_CREAT)

Other documentation in

man 2 shmget 

See also

https://man.cx/shmget(2)

pshmctl()

int pshmctl	(	int	shmid,
		int	cmd,
		struct shmid_ds *	buf
	)

shmctl wrapper function.

Other documentation in

man 2 shmctl 

See also

https://man.cx/shmctl(2)

pshmat()

void* pshmat	(	int	shmid,
		const void *	shmaddr,
		int	shmflg
	)

shmat wrapper function.

Other documentation in

man 2 shmat 

See also

https://man.cx/shmat(2)

pshmdt()

void pshmdt

(

const void *

shmaddr

)

shmdt wrapper function.

Other documentation in

man 2 shmdt 

See also

https://man.cx/shmdt(2)

psemget()

int psemget	(	key_t	key,
		int	nsems,
		int	semflg
	)

semget wrapper function.

Precondition:

nsems > 0

Other documentation in

man 2 semget 

See also

https://man.cx/semget(2)

psemctl()

int psemctl	(	int	semid,
		int	semnum,
		int	cmd
	)

semctl wrapper function.

Other documentation in

man 2 semctl 

See also

https://man.cx/semctl(2)

psemop()

void psemop	(	int	semid,
		struct sembuf *	sops,
		size_t	nsops
	)

semop wrapper function.

Other documentation in

man 2 semop 

See also

https://man.cx/semop(2)

pmsgget()

int pmsgget	(	key_t	key,
		int	msgflg
	)

msgget wrapper function.

Other documentation in

man 2 msgget 

See also

https://man.cx/msgget(2)

pmsgctl()

int pmsgctl	(	int	msqid,
		int	cmd,
		struct msqid_ds *	buf
	)

msgctl wrapper function.

Other documentation in

man 2 msgctl 

See also

https://man.cx/msgctl(2)

pmsgsnd()

void pmsgsnd	(	int	msqid,
		const void *	msgp,
		size_t	msgsz,
		int	msgflg
	)

msgsnd wrapper function.

Other documentation in

man 2 msgsnd 

See also

https://man.cx/msgsnd(2)

pmsgrcv()

size_t pmsgrcv	(	int	msqid,
		void *	msgp,
		size_t	msgsz,
		long	msgtyp,
		int	msgflg
	)

msgrcv wrapper function.

Other documentation in

man 2 msgrcv 

See also

https://man.cx/msgrcv(2)

psem_open()

sem_t* psem_open	(	const char *	name,
		int	oflag
	)

sem_open wrapper function.

Other documentation in

man 3 sem_open 

See also

https://man.cx/sem_open(3)

psem_close()

void psem_close

(

sem_t *

sem

)

sem_close wrapper function.

Precondition:

sem != NULL

Other documentation in

man 3 sem_close 

See also

https://man.cx/sem_close(3)

psem_unlink()

void psem_unlink

(

const char *

name

)

sem_unlink wrapper function.

Other documentation in

man 3 sem_unlink 

See also

https://man.cx/sem_unlink(3)

psem_init()

void psem_init	(	sem_t *	sem,
		int	pshared,
		unsigned int	value
	)

sem_init wrapper function.

Precondition:

sem != NULL

Other documentation in

man 3 sem_init 

See also

https://man.cx/sem_init(3)

psem_destroy()

void psem_destroy

(

sem_t *

sem

)

sem_destroy wrapper function.

Precondition:

sem != NULL

Other documentation in

man 3 sem_destroy 

See also

https://man.cx/sem_destroy(3)

psem_wait()

void psem_wait

(

sem_t *

sem

)

sem_wait wrapper function.

Precondition:

sem != NULL

Other documentation in

man 3 sem_wait 

See also

https://man.cx/sem_wait(3)

psem_trywait()

int psem_trywait

(

sem_t *

sem

)

sem_trywait wrapper function.

Precondition:

sem != NULL

Other documentation in

man 3 sem_trywait 

See also

https://man.cx/sem_trywait(3)

Returns

true (!=0) on success, false (0) if semaphore is zero

psem_timedwait()

int psem_timedwait	(	sem_t *	sem,
		const struct timespec *	abs_timeout
	)

sem_timedwait wrapper function.

Precondition:

sem != NULL

Other documentation in

man 3 sem_timedwait 

See also

https://man.cx/sem_timedwait(3)

Returns

true (!=0) on success, false (0) if timeout has expired before being able to decrement the semaphore

psem_post()

void psem_post

(

sem_t *

sem

)

sem_post wrapper function.

Precondition:

sem != NULL

Other documentation in

man 3 sem_post 

See also

https://man.cx/sem_post(3)

ppipe()

void ppipe

(

int

pipefd[2]

)

pipe wrapper function.

Other documentation in

man 3 pipe 

See also

https://man.cx/pipe

ppopen()

FILE* ppopen	(	const char *	command,
		const char *	type
	)

popen wrapper function.

Precondition:

command != NULL type != NULL

Other documentation in

man 3 popen 

See also

https://man.cx/popen

ppclose()

void ppclose

(

FILE *

stream

)

pclose wrapper function.

Precondition:

stream != NULL

Other documentation in

man 3 pclose 

See also

https://man.cx/pclose