linux编程，进程的通信

#include <sys/types.h>

#include <sys/msg.h>

#include <unistd.h>

void msg_stat(int,struct msqid_ds )

main()

{

int gflags,sflags,rflags

key_t key

int msgid

int reval

struct msgsbuf{

int mtype

char mtext[1]

}msg_sbuf

struct msgmbuf

{

int mtype

char mtext[10]

}msg_rbuf

struct msqid_ds msg_ginfo,msg_sinfo

char* msgpath="/unix/msgqueue"

key=ftok(msgpath,'a')

gflags=IPC_CREAT|IPC_EXCL

msgid=msgget(key,gflags|00666)

if(msgid==-1)

{

printf("msg create error\n")

return

}

//创建一个消息队列后，输出消息队列缺省属性

msg_stat(msgid,msg_ginfo)

sflags=IPC_NOWAIT

msg_sbuf.mtype=10

msg_sbuf.mtext[0]='a'

reval=msgsnd(msgid,&msg_sbuf,sizeof(msg_sbuf.mtext),sflags)

if(reval==-1)

{

printf("message send error\n")

}

//发送一个消息后，输出消息队列属性

msg_stat(msgid,msg_ginfo)

rflags=IPC_NOWAIT|MSG_NOERROR

reval=msgrcv(msgid,&msg_rbuf,4,10,rflags)

if(reval==-1)

printf("read msg error\n")

else

printf("read from msg queue %d bytes\n",reval)

//从消息队列中读出消息后，输出消息队列属性

msg_stat(msgid,msg_ginfo)

msg_sinfo.msg_perm.uid=8//just a try

msg_sinfo.msg_perm.gid=8//

msg_sinfo.msg_qbytes=16388

//此处验证超级用户可以更改消息队列的缺省msg_qbytes

//注意这里设置的值大于缺省值

reval=msgctl(msgid,IPC_SET,&msg_sinfo)

if(reval==-1)

{

printf("msg set info error\n")

return

}

msg_stat(msgid,msg_ginfo)

//验证设置消息队列属性

reval=msgctl(msgid,IPC_RMID,NULL)//删除消息队列

if(reval==-1)

{

printf("unlink msg queue error\n")

return

}

}

void msg_stat(int msgid,struct msqid_ds msg_info)

{

int reval

sleep(1)//只是为了后面输出时间的方便

reval=msgctl(msgid,IPC_STAT,&msg_info)

if(reval==-1)

{

printf("get msg info error\n")

return

}

printf("\n")

printf("current number of bytes on queue is %d\n",msg_info.msg_cbytes)

printf("number of messages in queue is %d\n",msg_info.msg_qnum)

printf("max number of bytes on queue is %d\n",msg_info.msg_qbytes)

//每个消息队列的容量（字节数）都有限制MSGMNB，值的大小因系统而异。在创建新的消息队列时，//msg_qbytes的缺省值就是MSGMNB

printf("pid of last msgsnd is %d\n",msg_info.msg_lspid)

printf("pid of last msgrcv is %d\n",msg_info.msg_lrpid)

printf("last msgsnd time is %s", ctime(&(msg_info.msg_stime)))

printf("last msgrcv time is %s", ctime(&(msg_info.msg_rtime)))

printf("last change time is %s", ctime(&(msg_info.msg_ctime)))

printf("msg uid is %d\n",msg_info.msg_perm.uid)

printf("msg gid is %d\n",msg_info.msg_perm.gid)

}