공간사랑

/**********************************************************************/

#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/msg.h>

/* 접근 가능하고 실제로 존재하는 파일의 경로와 프로젝트 식별자를 key_t 타입의 IPC 키 값으로 변환 */
key_t ftok (__const char *__pathname, int __proj_id);

int msgget ( key_t key, int msgflg );
int msgctl ( int msqid, int  cmd, struct msqid_ds *buf );

int msgsnd ( int msqid, const void *msgp, size_t msgsz, int msgflg );
ssize_t msgrcv ( int msqid, void *msgp, size_t msgsz, long msgtype, int msgflg );

<msgget>

/* queue의 key가 존재하는지 체크 : 이미 생성된 message queue ID를 return 함. 없으면 오류로 -1을 return 함. */

msqid = msgget ( key, 0 );

/* queue의 key 생성 : queue가 없으며 새로 생성하고 있으면 오류로 -1을 return 함. 접근 권한은 0666 */

msqid = msgget( key, IPC_CREAT | IPC_EXCL | 0666 );

/* queue의 key 생성 : queue가 없으며 새로 생성하고 이미 생성되어 있으면 이미 생성되어 있는 message queue ID를 return 함. */

msqid = msgget( key, IPC_CREAT | 0666 );

<msgctl>

message queue 정보를 조회, 변경, 삭제 작업 수행.( IPC_STAT, IPC_SET, IPC_RMID )

/* msqid 메시지 큐 정보를 얻어 msg_stat에 저장 */

struct msqid_ds msg_stat;
msgctl( msqid, IPC_STAT, &msg_stat );

struct msqid_ds
{
  struct ipc_perm msg_perm;     /* structure describing operation permission */
  __time_t msg_stime;           /* time of last msgsnd command */
#if __WORDSIZE == 32
  unsigned long int __unused1;
#endif
  __time_t msg_rtime;           /* time of last msgrcv command */
#if __WORDSIZE == 32
  unsigned long int __unused2;
#endif
  __time_t msg_ctime;           /* time of last change */
#if __WORDSIZE == 32
  unsigned long int __unused3;
#endif
  unsigned long int __msg_cbytes; /* current number of bytes on queue */
  msgqnum_t msg_qnum;           /* number of messages currently on queue */
  msglen_t msg_qbytes;          /* max number of bytes allowed on queue */
  __pid_t msg_lspid;            /* pid of last msgsnd() */
  __pid_t msg_lrpid;            /* pid of last msgrcv() */
  unsigned long int __unused4;
  unsigned long int __unused5;
};

/****

struct ipc_perm
{
    __key_t __key;                      /* Key.  */
    __uid_t uid;                        /* Owner's user ID.  */
    __gid_t gid;                        /* Owner's group ID.  */
    __uid_t cuid;                       /* Creator's user ID.  */
    __gid_t cgid;                       /* Creator's group ID.  */
    unsigned short int mode;            /* Read/write permission.  */
    unsigned short int __pad1;
    unsigned short int __seq;           /* Sequence number.  */
    unsigned short int __pad2;
    unsigned long int __unused1;
    unsigned long int __unused2;
};

/* 큐의 msqid_ds 구조체의 값을 설정 변경 */

msgctl( msqid, IPC_SET, &msg_stat );

/* message queue 삭제 */

msgctl ( msqid, IPC_RMID, (struct msqid_ds *)NULL );

<msgsnd>

struct my_queue_msg_form {
        long msgtype;
        char mtext[1024];
};

struct my_queue_msg_form qbuf;

qbuf.msgtype = 100;
sprintf(qbuf.mtext, "1234");

msgsnd ( msqid, &qbuf, sizeof(qbuf.mtext), 0 );

<msgrcv>

msgtype = 100;

msgrcv ( msqid, &qbuf, sizeof(qbuf.mtext), msgtype, 0 );

/**********************************************************************/

# include <sys/types.h>
# include <sys/ipc.h>
# include <sys/sem.h>

int semget ( key_t key, int semnum, int semflg );

int semctl ( int semid, int semnum, int cmd, union semun arg );

int semop ( int semid, struct sembuf *sops, unsigned nsops );

//
// /* semop 시스템 호출은 이러한 배열을 갖는다 */
// struct sembuf {
//    ushort  sem_num;        /* 배열안에서의 세마포어 인덱스 */
//    short   sem_op;         /* 수행할 동작 (양수,음수, 또는 0) */
//    short   sem_flg;        /* 동작 플래그 */
// };
//

/* 세마포어 조회 */
semid = semget(key, 0, 0666);

/* 생성 */
semid = semget(key, semnum, IPC_CREAT | IPC_EXCL | 0666);

/* lock */
struct sembuf sem_lock = { 0, -1, IPC_NOWAIT };

semop(sid, &sem_lock, 1);

/* unlock */
struct sembuf sem_unlock = { 0, 1, IPC_NOWAIT };

semop(sid, &sem_unlock, 1);

/* 조회 */
union semun semopts;

semctl(semid, 0, IPC_STAT, semopts);

/* 변경 */
semctl(semid, 0, IPC_SET, semopts);

/* 삭제 */
semctl(semid, 0, IPC_RMID, 0);

/**********************************************************************/

#include <sys/ipc.h>
#include <sys/shm.h>

int shmget ( key_t key, int size, int shmflg );

int shmctl ( int shmid, int cmd, struct shmid_ds *buf );

void *shmat ( int shmid, const void *shmaddr, int shmflg );

int shmdt ( const void *shmaddr );

/* 생성 */
#define SHMSIZE 100

shmid = shmget(key, SHMSIZE, 0);

shmid = shmget(key, SHMSIZE, IPC_CREAT | IPC_EXCL | 0666);

/* Data structure describing a shared memory segment.  */
struct shmid_ds
  {
    struct ipc_perm shm_perm;           /* operation permission struct */
    size_t shm_segsz;                   /* size of segment in bytes */
    __time_t shm_atime;                 /* time of last shmat() */
#if __WORDSIZE == 32
    unsigned long int __unused1;
#endif
    __time_t shm_dtime;                 /* time of last shmdt() */
#if __WORDSIZE == 32
    unsigned long int __unused2;
#endif
    __time_t shm_ctime;                 /* time of last change by shmctl() */
#if __WORDSIZE == 32
    unsigned long int __unused3;
#endif
    __pid_t shm_cpid;                   /* pid of creator */
    __pid_t shm_lpid;                   /* pid of last shmop */
    shmatt_t shm_nattch;                /* number of current attaches */
    unsigned long int __unused4;
    unsigned long int __unused5;
  };

/* 조회 */
struct shmid_ds myshmds;

shmctl(shmid, IPC_STAT, &myshmds);

/* 변경 */
shmctl(shmid, IPC_SET, &myshmds);

/* 삭제 */
shmctl(shmid, IPC_RMID, 0);