为什么凡科网做的网站无法搜索,手机网站策划,asp网站开发 知识,如何查询域名注册人信息一、System V 信号量
1.信号量linux命令
显示#xff1a;
ipcs -a 显示所有共享内核对象
ipcs -s 显示信号量 s semphore删除#xff1a;
ipcrm -s ID 删除信号量 二、主要函数应用
1. 函数原型#xff1a;
#include sys/sem.h
int semget(key_t key, int …一、System V 信号量
1.信号量linux命令
显示
ipcs -a 显示所有共享内核对象
ipcs -s 显示信号量 s semphore删除
ipcrm -s ID 删除信号量 二、主要函数应用
1. 函数原型
#include sys/sem.h
int semget(key_t key, int nsems, int flag);参数
key信号集的名字nsems信号集中信号量的个数semflg由九个权限标志构成它们的用法和创建文件时用的mode模式标志是一样的。2. 函数原型
#include sys/sem.h
int semctl(int semid. int semnum, int cmd, ..../*union semun arg*/);
参数
semid由semget返回的信号集标识码semnum信号集中信号量的序号cmd将要采取的动作有三个可能取值最后一个参数根据命令不同而不同
cmd
命令说明SETVAL设置信号量集中信号量的计数值GETVAL获取信号集中的信号量的计数值IPC_STAT对此集合取semid_ds结构并存储在arg.buf指向的结构中IPC_SET在进程有足够权限的前提下把信号集中的当前关联值设置为semid_ds 数据结构中给出的值IPC_RMID删除信号集3. 函数原型
#include sys/sem.h
int semop(int semid, struct sembuf semoparray[], size_t nops);
参数
semid是该信号集量的标识码ID也是semget函数的返回值。sops是一个指向结构体的指针nsops操作的信号量的个数三、程序清单
#include sys/sem.h
#include unistd.h
#include stdio.h
#include stdlib.h#define ERR_EXIT(m) do { perror(m), exit(EXIT_FAILURE); }while(0)
union semun
{int val;struct semid_ds *buf;unsigned short *array;
};int sem_creat(key_t key)
{int semid;semid semget(key, 1, IPC_CREAT | IPC_EXCL | 0666);if (semid -1)ERR_EXIT(semget);return semid;
}int sem_open(key_t key)
{int semid;semid semget(key, 0, 0);if (semid -1)ERR_EXIT(semget);return semid;
}int sem_setval(int semid, int val)
{union semun su;su.val val;int ret;ret semctl(semid, 0, SETVAL, su);if (ret -1)ERR_EXIT(sem_setval);return 0;
}
int sem_getval(int semid)
{int ret;ret semctl(semid, 0, GETVAL, 0);if (semid -1)ERR_EXIT(sem_getval);printf(current val is %d\n, ret);return ret;
}int sem_d(int semid)
{int ret;ret semctl(semid, 0, IPC_RMID, 0);if (ret -1)ERR_EXIT(semctl);return 0;
}int sem_p(int semid)
{struct sembuf sb { 0, -1, 0 };int ret;ret semop(semid, sb, 1);if (ret -1)ERR_EXIT(semop); return ret;
}int sem_v(int semid)
{struct sembuf sb { 0, 1, 0 };int ret;ret semop(semid, sb, 1);if (ret -1)ERR_EXIT(semop); return ret;
}int sem_getmode(int semid)
{union semun su;struct semid_ds sem;su.buf sem;int ret semctl(semid, 0, IPC_STAT, su);if (ret -1)ERR_EXIT(semctl);printf(currcnt pcrmissions id %o\n, su.buf-sem_perm.mode);return ret;
}int sem_setmode(int semid, char *mode)
{union semun su;struct semid_ds sem;su.buf sem;int ret semctl(semid, 0, IPC_STAT, su);if (ret -1)ERR_EXIT(semctl);printf(cuttent permissions is %o\n, su.buf-sem_perm.mode);sscanf(mode, %o, (unsigned int*)su.buf-sem_perm.mode);ret semctl(semid, 0, IPC_SET, su);if (ret -1)ERR_EXIT(semctl);printf(permissins updated...\n);
}void usage(void)
{fprintf(stderr, usage\n);fprintf(stderr, semtool -c\n);fprintf(stderr, semtool -d\n);fprintf(stderr, semtool -p\n);fprintf(stderr, semtool -v\n);fprintf(stderr, semtool -s val\n);fprintf(stderr, semtool -q\n);fprintf(stderr, semtool -f\n);fprintf(stderr, semtool -m mode\n);
}int main(int argc, char *argv[])
{int opt;opt getopt(argc, argv, cdpvs:gfm:);if (opt ?)exit(EXIT_FAILURE);if (opt -1){usage();exit(EXIT_FAILURE);}key_t key ftok(., s);int semid;switch (opt){casec:sem_creat(key);break;casep:semid sem_open(key);sem_p(semid);sem_getval(semid);break;casev:semid sem_open(key);sem_v(semid);sem_getval(semid);break;cased:semid sem_open(key);sem_d(semid);break;cases:semid sem_open(key);sem_setval(semid, atoi(optarg));break;caseg:semid sem_open(key);sem_getval(semid);break;casef:semid sem_open(key);sem_getmode(semid);break;casem:semid sem_open(key);sem_setmode(semid, argv[2]);break;}return 0;
} 四、参考资料
getopt函数用法
