Linux multi-process + semaphore + shared memory programming

This program implements data communication between two processes that are not related to each other through shared memory.

At the same time, the signal volume is used to guarantee the read and write synchronization of two processes: the receiver cannot read the data while the sender is writing the shared memory, and the sender cannot write the data when the receiver reads the data.

1. Fork Create Child process

2, using two yuan signal, synchronous read-write end

Fork_shm.c

#include <stdio.h> #include <sys/types.h> #include <unistd.h> #include "send_recv.h" int main (void) { printf ("fork test!\n");p id_t pid;if ((Pid=fork ()) ==-1) printf ("Fork Error"), else if (pid==0) {printf ("in the process\n ");p rintf (" The Father process ' s ppid is%d\n ", getppid ()); Fork_recv ();} Else{//sleep (1);p rintf ("In the parent process\n");p rintf ("The son process's PID is%d\n", getpid ()); Fork_send ();} return 0;}

Send_recv.c

#include "fork_recv.c" #include "fork_send.c" int fork_recv (); int fork_send ();

Fork_send.c

#include <stdio.h> #include <stdlib.h> #include <unistd.h> #include <sys/types.h> #include < sys/shm.h> #include <sys/ipc.h> #include <sys/sem.h> #include <string.h>int fork_send () {int Running=1;int shid;int semid;int value;void *sharem=null;struct sembuf sem_b;sem_b.sem_num = 0;SEM_B.SEM_FLG = SEM_UNDO; if ((Semid=semget (key_t) 123456,1,0666| Ipc_creat) ==-1) {perror ("Semget"); exit (exit_failure);}        if (Semctl (semid, 0, setval, 0) = =-1) {printf ("SEM init error"); if (Semctl (semid,0,ipc_rmid,0)!=0) {perror ("Semctl"); exit (exit_failure);} Exit (exit_failure);} Shid=shmget (key_t) 654321, (size_t) 2048,0600| Ipc_creat), if (shid==-1) {perror ("Shmget"); exit (exit_failure);} Sharem=shmat (shid,null,0); if (sharem==null) {perror ("Shmat"); exit (exit_failure);} while (running) {if ((Value=semctl (semid, 0, Getval) ==0) {printf ("Write Data operate\n");p rintf ("Please input something : \ n "); scanf ("%s ", Sharem), Sem_b.sem_op = 1;if (Semop (Semid, &sem_b, 1) = =-1) {fprintf (stderr, "Semaphore_p failed\n"); exit (exit_failure);}} if (strcmp (Sharem, "end") ==0) running--;} SHMDT (sharem); return 0;}

Fork_recv.c

#include <stdio.h> #include <stdlib.h> #include <sys/types.h> #include <unistd.h> #include < string.h> #include <sys/ipc.h> #include <sys/shm.h> #include <sys/sem.h>int fork_recv () {int Running=1;char *shm_p=null;int shmid;int semid;int value;struct sembuf sem_b;sem_b.sem_num = 0;SEM_B.SEM_FLG = SEM_UNDO; if ((Semid=semget (key_t) 123456,1,0666| Ipc_creat) ==-1) {perror ("Semget"); exit (exit_failure);} Shmid=shmget (key_t) 654321, (size_t) 2048,0600| Ipc_creat), if (shmid==-1) {perror ("Shmget"); exit (exit_failure);} Shm_p=shmat (shmid,null,0); if (shm_p==null) {perror ("Shmat"); exit (exit_failure);} while (running) {if ((Value=semctl (semid, 0, Getval) ==1) {printf ("read Data operate\n"); sem_b.sem_op = -1;if (Semop ( Semid, &sem_b, 1) = =-1) {fprintf (stderr, "semaphore_p failed\n"); exit (exit_failure);} printf ("%s\n", shm_p);} if (strcmp (shm_p, "end") ==0) running--;} SHMDT (shm_p); if (Shmctl (shmid,ipc_rmid,0)!=0) {perror ("Shmctl"); exit (exit_failure);} if (Semctl (semid,0,ipc_rmid,0)! =0) {perror ("Semctl"); exit (exit_failure);} return 0;}

Linux multi-process + semaphore + shared memory programming