Linux application Development-process communication (IPC)

Ipc

Why

1. Data transfer

2. Resource Sharing

Objective:

3. Notification events

4. Process Control

Development:

1.UNIX interprocess Communication

2. Based on system V

3.POSIX

Way classification:

1.pipe (pipe) FIFO (named pipe)

2.signal

3. Message Queuing

4. Shared Memory

5. Signal Volume

6. Socket (socket)

Pipeline communication: Unidirectional, FIFO

Create

Pipe: Communication between father and son

FIFO: Any

Create:

int pipe (int filedis[2]);

When a pipeline is created, two file descriptors are generated: filedis[0] read pipeline, Filedid[1] write pipeline.

Shut down:

Close (filedis[1,2])

Close two descriptors

Pipe Reading and writing:

Parent process Write filedis[1], child process read Filedis[0]

Fork must be created again before pipe.

Famous pipeline: FIFO

Create

#include <sys/types.h>

#include <sys/stat.h>

int Mkfifo (const char*pathname,mode_t mode);

Pathname:fifo file name

Mode: Properties

Operation

When FIFO is turned on, flag (O_nonblock)

1. When not in use: The process is blocked when access is not met

2. Use: Access cannot be met without blocking, immediately error return, Error=enxio

Signal communication:

Signal type: (30 kinds)

E:

Sigint:crtl+c

SIGKILL:

Processing

1. Ignore

Sigkill,sigstop can't ignore

2. Perform the actions desired by the user

3. Perform default actions (mostly ignored)

Signal

#include <signal.h>

void (*signal (int signo,void (*fun) (int))) (int)//How to understand??

Func may take value:

1.SIG_LGN: Ignore this signal

2.SIG_DFL: by system default mode

3. Signal Processing function Name: Use this function to handle

Shared Memory:

Shared part of physical memory by multiple processes

Fast, no additional access functions required

Realize:

1. Create Shmget ()

2. Mapping to a specific process Shmat ()

int Shmget (key_t key,int size,int SHMFLG)

Key: Shared Memory key value

0/ipc_private created new memory, successfully returned the shared memory identifier, failed loopback-1.

int Shmat (int shmid,char*shmaddr,int flag)

Shmid: Shared Memory identifier

Flag: Determines in what way to determine the mapping address, usually 0

The mapped address is returned successfully, and the failure returns-1.

Out:

int Shmdt (CHAR*AHMADDR)

Send:

Kill: Send to itself or to another process

Rasie: Self

#include <sys/types.h>

#include <signal.h>

int Kill (Pid_t,int Signo)

int Rasie (int signo)

Pid>0:

Pid==0: Same group

Pid<0: A process sent to its process group ID equals |pid|

Pid==-1: All Processes

Alarm

unsigned int alarm (unsigned int seconds);

After a predetermined time, the SIGALRM signal is generated, and if not captured, the process is terminated.

Pause

Causes the process call to hang until a signal is received

int pause (void)

Only after a signal processing function has been executed does the hang end.

Signal Processing

Linux application Development-process communication (IPC)