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三种系统V IPC
消息队列：
消息队列是消息的链接表 ,存放在内核中并由消息队列标识符标识。
消息队列：
同一块物理内存被映射到进程A、B各自的进程地址空间。
进程A可以即时看到进程B对共享内存中数据的更新，反之亦然。
由于多个进程共享同一块内存区域，必然需要某种同步机制，互斥锁和信号量都可以。
信号量：
可以被多个进程共享的变量。（信号是cpu发给所以进程的通知，进程是否接受，是否处理要看进程本身）
消息队列：
key = ftok("./7-1",'b');
msgid = msgget(key, IPC_CREAT | 0666);
len = msgsnd(msgid,(void *)&sndbuf,100,0);
rcvLen=msgrcv(msgid,(void *)&rcvbuf,100,1,0);
共享内存：
key=ftok("write.c",0x00);
shmid=shmget(key,512,IPC_CREAT|0600 ) ;
shmaddr=(book *)shmat(shmid,NULL,0);
shmdt(shmaddr); //断开映射
信号量：
key= ftok("mysem",'s');
sem_id= semget(key,2,IPC_CREAT|0644);
ret= semctl(sem_id,0,SETALL,arg);
semop(sem_id,(struct sembuf*)&sops[1],1);
semctl(sem_id,0,IPC_RMID);
进程间通信----消息队列
write.c
#include <stdio.h>
#include <sys/msg.h>
#include <string.h>
typedef struct msgque
{
long type; //long型的type标识
char content[100];
}mq;
int main()
{
int key;
int msgid;
mq sndbuf;
int rcvLen;
int flag=1;
key = ftok("./7-1",'b');
msgid = msgget(key, IPC_CREAT | 0666); //建消息队列
if(msgid==-1)
printf("error\n");
while(1)
{
printf("send输入: ");
fgets(sndbuf.content,100, stdin);
if(strncmp(sndbuf.content,"end",3)==0)
flag=0;
sndbuf.type = 1;
msgsnd(msgid,(void *)&sndbuf,100,0);//发送给消息队列
sleep(1);
if(flag==0)
return 0;
}
return 0;
}
#include <stdio.h>
#include <sys/msg.h>
#include <string.h>
typedef struct msgque
{
long type; //long型的type标识
char content[100];
}mq;
int main()
{
int key;
int msgid;
mq rcvbuf;
int rcvLen;
key = ftok("./7-1",'b');
msgid = msgget(key, IPC_CREAT | 0666); //建消息队列
if(msgid==-1)
printf("error\n");
while(1)
{
rcvLen=msgrcv(msgid,(void *)&rcvbuf,100,1,0);
if(strncmp(rcvbuf.content,"end",3)!=0)
{
printf("receive接受：%s",rcvbuf.content);
}
else
{
printf("结束\n");
return 0;
}
}
return 0;
}
进程间通信----共享内存
write.c
/*共享内存实现进程通信
key=ftok("write.c",0x00); //两个非亲缘进程用同一个key
int shmid = shmget(key, 512, IPC_CREAT|0600);ipc_private(亲缘间代替key)
char *shmaddr;
写端：shmaddr = (char *)shmat(shmid,NULL,0);
//id与内存绑定，然后写shmaddr
shmdt(shmaddr); //关闭后让读端读
读端：shmaddr=(char *)shmat(shmid,NULL,0);
*/
#include<stdio.h>
#include<stdlib.h>
#include<unistd.h>
#include<sys/ipc.h>
#include<sys/shm.h>
#include<error.h>
#include<string.h>
#include<sys/types.h>
typedef struct book
{
char no[8];
char name[8];
double price;
}book;
int main(void)
{
int shmid;
key_t key;
book *shmaddr;
book allbook [2]={ {"001","math",12.5},
{"002","math",13.5}
};
key=ftok("write.c",0x00); //建shm
if(key==-1){
perror("key error\n");
return -1;
}
printf("key=%d\n",key);
shmid=shmget(key,512,IPC_CREAT|0600 ) ;
if (shmid<0){
perror("shmid get error\n") ;
return -1 ;
}
printf("shmid =%d\n",shmid); //连shm
shmaddr=(book *)shmat(shmid,NULL,0);
if(shmaddr<(book *)0){
perror("shmat addr error\n");
return -1;
}
memcpy(shmaddr,allbook,sizeof(book)*2);
int i;
for(i=0;i<2;i++)
{
printf("no:%s,",(*(shmaddr+i)).no);
printf("name:%s,",shmaddr[i].name);
printf("price:%lf\n",shmaddr[i].price);
}
shmdt(shmaddr);
return 0 ;
}
read.c
#include<stdio.h>
#include<stdlib.h>
#include<unistd.h>
#include<sys/ipc.h>
#include<sys/shm.h>
#include<error.h>
#include<string.h>
#include<sys/types.h>
typedef struct book
{
char no[8];
char name[8];
double price;
}book;
int main(void)
{
int shmid,i;
key_t key;
book *shmaddr;
key=ftok("write.c",0x00); //建shm
if(key==-1){
perror("key error\n");
return -1;
}
printf("key=%d\n",key);
shmid=shmget(key,512,IPC_CREAT|0600 ) ;
if (shmid<0){
perror("shmid get error\n") ;
return -1 ;
}
printf("shmid =%d\n",shmid); //连shm
shmaddr=(book *)shmat(shmid,NULL,0);
if(shmaddr<(book *)0){
perror("shmat addr error\n");
return -1;
}
for(i=0;i<2;i++)
{
printf("no:%s,",(*(shmaddr+i)).no);
printf("name:%s,",shmaddr[i].name);
printf("price:%lf\n",shmaddr[i].price);
}
shmdt(shmaddr);
return 0 ;
}
进程间通信----信号量
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/sem.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/ipc.h>
int sem_id;
void init()
{
key_t key;
int ret;
unsigned short sem_array[2];
union semun
{
int val;
struct semid_ds *buf;
unsigned short *array;
}arg;
key= ftok("mysem",'s');
sem_id= semget(key,2,IPC_CREAT|0644);
sem_array[0]= 0;
sem_array[1]= 100;
arg.array = sem_array;
ret= semctl(sem_id,0,SETALL,arg);
if(ret== -1)
{
printf("SETALL failed (%d)\n",errno);
}
printf("productor init is %d\n",semctl(sem_id,0,GETVAL));//getval
printf("space init is %d\n\n",semctl(sem_id,1,GETVAL));
}
void del()
{
semctl(sem_id,0,IPC_RMID);
}
int main(int argc,char *argv[])
{
struct sembuf sops[2];
sops[0].sem_num= 0;
sops[0].sem_op= 1;
sops[0].sem_flg= 0;
sops[1].sem_num= 1;
sops[1].sem_op= -1;
sops[1].sem_flg= 0;
init();
printf("以下为生产者\n");
while(1)
{
printf("\n输出前：\n");
printf("productor number is %d\n",semctl(sem_id,0,GETVAL));
printf("space number is %d\n",semctl(sem_id,1,GETVAL));
semop(sem_id,(struct sembuf*)&sops[1],1);
printf("now producing...\n");
semop(sem_id,(struct sembuf*)&sops[0],1);
printf("\nafter produce\n");
printf("space number is %d\n",semctl(sem_id,1,GETVAL));
printf("productor number is %d\n",semctl(sem_id,0,GETVAL));
sleep(2);
}
del();
return 0;
}
//sem_customer.c
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/sem.h>
#include <errno.h>
int sem_id;
void init()
{
key_t key;
key=ftok("mysem",'s');
sem_id= semget(key,2,IPC_CREAT|0644);
}
int main(int argc,char *argv[])
{
struct sembuf sops[2];
sops[0].sem_num= 0;
sops[0].sem_op= -1;
sops[0].sem_flg= 0;
sops[1].sem_num= 1;
sops[1].sem_op= 1;
sops[1].sem_flg= 0;
init();
printf("this is customer\n");
while(1)
{
printf("\n\nbefore consume:\n");
int ret= semctl(sem_id,0,GETVAL);
int ret1= semctl(sem_id,1,GETVAL);
printf("productor is %d\n",ret);
printf("space is %d\n",ret1);
semop(sem_id,(struct sembuf*)&sops[0],1);
printf("now consuming...\n");
semop(sem_id,(struct sembuf*)&sops[1],1);
printf("\nafter consume\n");
printf("productor number is %d\n",semctl(sem_id,0,GETVAL));
printf("space number is %d\n",semctl(sem_id,1,GETVAL));
sleep(3);
}
return 0;
}