linux環(huán)境進(jìn)程間通信(三)：消息隊(duì)列(存儲(chǔ)版)
【正文】 e crosses the boundary layer (called the tropopause),e can expect a lot of turbulence.The supersonic descent could happen as early as Sunda.The weatheThe balloon will slowly drift to the edge of space at 120,000 feet ( Then, I would assume, he will slowly step out onto something resembling an Olympic diving platform.Below, the Earth bees the concrete bottom of a swimming pool that he wants to land on, but not too hard. Still, he39。t start planning... Those years, those days of do, finally, like youth, will end in our life. 此刻，天空是陰暗的，空氣里有著剛下過(guò)雨之后的清新因子。想要的，不想要的，界限明確，好像沒(méi)有什么可以撼動(dòng)自己。 Junior high school, thought to have a crush on just means that the real growth, but over the past three years later, his writing of alumni in peace, suddenly found that isn39。s governing body, has also ordered an immediate investigation into the referee39。s antiracism taskforce, is in London for the Football Association39。damagesbased agreement. In England and Wales, your solicitor can39。t agree with the disciplinary action your employer has taken against you對(duì)POSIX以及系統(tǒng)V消息隊(duì)列都有闡述，對(duì)Linux環(huán)境下的程序開發(fā)有極大的啟發(fā)意義。 /* current number of bytes on queue */ unsigned short msg_qnum。 struct msg *msg_first。 /* number of messages in queue */ unsigned long q_qbytes。如管道和有名管道； 2. 隨內(nèi)核持續(xù)：IPC一直持續(xù)到內(nèi)核重新自舉或者顯示刪除該對(duì)象為止。()))。//每個(gè)消息隊(duì)列的容量（字節(jié)數(shù)）都有限制MSGMNB，值的大小因系統(tǒng)而異。//只是為了后面輸出時(shí)間的方便reval=msgctl(msgid,IPC_STAT,amp。if(reval==1){ printf(msg set info error\n)。if(reval==1) printf(read msg error\n)。a39。gflags=IPC_CREAT|IPC_EXCL。struct msgmbuf { int mtype。include sys/include sys/include void msg_stat(int,struct msqid_ds )。1. IPC_STAT：該命令用來(lái)獲取消息隊(duì)列信息，返回的信息存貯在buf指向的msqid結(jié)構(gòu)中； 2. IPC_SET：該命令用來(lái)設(shè)置消息隊(duì)列的屬性，要設(shè)置的屬性存儲(chǔ)在buf指向的msqid結(jié)構(gòu)中；可設(shè)置屬性包括：、同時(shí)，也影響msg_ctime成員。向msgid代表的消息隊(duì)列發(fā)送一個(gè)消息，即將發(fā)送的消息存儲(chǔ)在msgp指向的msgbuf結(jié)構(gòu)中，消息的大小由msgze指定。 IPC_NOWAIT 如果沒(méi)有滿足條件的消息，調(diào)用立即返回，此時(shí)，errno=ENOMSG 在以下兩種情況下，該調(diào)用將創(chuàng)建一個(gè)新的消息隊(duì)列：原因如下： a39。char mtext[1]。 //該鍵值則唯一對(duì)應(yīng)一個(gè)消息隊(duì)列 uid_t uid。因此系統(tǒng)中記錄消息隊(duì)列的數(shù)據(jù)結(jié)構(gòu)（struct ipc_ids msg_ids）位于內(nèi)核中，系統(tǒng)中的所有消息隊(duì)列都可以在結(jié)構(gòu)msg_ids中找到訪問(wèn)入口。消息隊(duì)列是隨內(nèi)核持續(xù)的（參見(jiàn)附錄 1）。消息隊(duì)列（也叫做報(bào)文隊(duì)列）能夠克服早期unix通信機(jī)制的一些缺點(diǎn)。在本系列專題的序（深刻理解Linux進(jìn)程間通信（IPC））中，提到對(duì)于消息隊(duì)列、信號(hào)燈、以及共享內(nèi)存區(qū)來(lái)說(shuō)，有兩個(gè)實(shí)現(xiàn)版本：POSIX的以及系統(tǒng)V的。隊(duì)列頭中包含了該消息隊(duì)列的大量信息，包括消息隊(duì)列鍵值、用戶ID、組ID、消息隊(duì)列中消息數(shù)目等等，甚至記錄了最近對(duì)消息隊(duì)列讀寫進(jìn)程的ID。gid_t cgid。因此，對(duì)于發(fā)送消息來(lái)說(shuō)，首先預(yù)置一個(gè)msgbuf緩沖區(qū)并寫入消息類型和內(nèi)容，調(diào)用相應(yīng)的發(fā)送函數(shù)即可；對(duì)讀取消息來(lái)說(shuō)，首先分配這樣一個(gè)msgbuf緩沖區(qū)，然后把消息讀入該緩沖區(qū)即可。 …linux為操作系統(tǒng)V進(jìn)程間通信的三種方式（消息隊(duì)列、信號(hào)燈、共享內(nèi)存區(qū)）提供了一個(gè)統(tǒng)一的用戶界面：int ipc(unsigned int call, int first, int second, int third, void *ptr, long fifth)。 int ipc(MSGSND, int first, int second, int third, void *ptr, long fifth)。 正如ipc手冊(cè)所說(shuō)的：ipc()是linux所特有的，編寫程序時(shí)應(yīng)注意程序的移植性問(wèn)題； 調(diào)用返回：成功返回消息隊(duì)列描述字，否則返回1。 msgrcv手冊(cè)中詳細(xì)給出了消息類型取不同值時(shí)(0。 當(dāng)前消息的大小與當(dāng)前消息隊(duì)列中的字節(jié)數(shù)之和超過(guò)了消息隊(duì)列的總?cè)萘浚?在后面的應(yīng)用實(shí)例中，輸出了redhat ，結(jié)果參見(jiàn)附錄 3。int msgid。struct msqid_ds msg_ginfo,msg_sinfo。 return。if(reval==1){ printf(message send error\n)。=8。//驗(yàn)證設(shè)置消息隊(duì)列屬性reval=msgctl(msgid,IPC_RMID,NULL)。 return。printf(last msgsnd time is %s, ctime(amp。}程序輸出結(jié)果見(jiàn)附錄 3。 time_t q_stime。 /* last receive pid */ struct list_head q_messages。 /* last msgsnd time */ __kernel_time_t msg_rtime。 /* pid of last msgsnd */ __kernel_ipc_pid_t msg_lrpid。 ta damagesbased agreement, you should make sure you39。s about how he felt and I would like to speak to him first to find out what his experience was.Uefa has May be back in the past, to oneself the paranoid weird belief disillusionment, these days, my mind has been very messy, in my mind constantly. Always feel oneself should go to do something, or write something. Twenty years of life trajectory deeply shallow, suddenly feel something, do it. 一字開頭的年齡已經(jīng)到了尾聲。t want to give vent to out your inner voice can be in the high school children of the feelings in a period, but was eventually infarction when graduation party in the throat, later aga
研究報(bào)告相關(guān)推薦
鄂ICP備17016276號(hào)-1