by信號(hào)量基本概P、V互斥：P、V同步：P、VS>0：Sstruct{int}P{if(s.value<0){將該進(jìn)程的PCBs.queue}}V{if(s.value<=0){}}信號(hào)量structsemid_dsstructipc_permsem_perm; /*Ownershipandpermissions*/ sem_otime;/*Lastsemoptime*/ sem_ctime;/*Lastchangetimeunsigned sem_nsems;/*No.ofsemaphoresinset#include#include#includeintsemget(key_tkey,intnsems,intsemintsemctl(intsemid,intsemnum,intcmd,intsemop(intsemid,structsembuf*sops,unsignedsemgetintsemget(key_tkey,intnsems,intkey:sem:由九個(gè)權(quán)限標(biāo)志構(gòu)成它們的用法和創(chuàng)建文件時(shí)使用的mode模式標(biāo)志是shmctlintsemctl(intsemid,intsemnum,intcmd,shmctlsemopintsemop(intsemid,structsembuf*sops,unsignedsemopsembufstructsembufshortsem_num;shortsem_op;shortsem_;sem_numsem_op是信號(hào)量一次PV操作時(shí)加減的數(shù)值，一般只會(huì)用到兩個(gè)值，一個(gè)是“-1”，P操作，等待信號(hào)量變得可用；另一個(gè)是“+1”V操作，發(fā)//{/*IPC_CREAT|IPC_EXCL不是O_CREAT|O_EXCL);intsemid=0;semid=semget(key,1,0666|O_CREAT|O_EXCL);if(semid==-1)returnintsemid=semget(key,1,0666|IPC_CREAT|IPC_EXCL);if(semid==-1)return}{intsemid=semget(key,0,0);if(semid==-1)returnsemid;}intsem_setval(intsemid,int{unionsemunsu;su.val=val;intret=semctl(semid,0,SETVAL,su);if(ret==-1)return}intsem_getval(intsemid,int{unionsemunsu;su.val=val;intret=semctl(semid,0,GETVAL,su);if(ret==-1)return}intsem_d(int{intret=semctl(semid,0,IPC_RMID,0);if(ret==-1)return}intsem_p(int{intret=struct sp={0,-1,ret= semop(semid&sp1)第三個(gè)參數(shù)是信號(hào)量的參數(shù)if(ret==-1)returnret;}intsem_v(int{struct sp={0,1,intret= semop(semid&sp1)第三個(gè)參數(shù)是信號(hào)量的參數(shù)if(ret==-1)return}intmain(intargc,char{int//semid=sem_c