Python: Difference between revisions
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* [[multiprocess.Lock replacement using SYSV]] |
* [[multiprocess.Lock replacement using SYSV]] |
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* [[Converting Gregorian dates to day numbers]] |
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<nowiki> |
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* [[numpy surprises]]] |
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#include <sys/types.h> |
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#include <sys/ipc.h> |
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#include <sys/sem.h> |
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#include <stdlib.h> |
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#include <stdio.h> |
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int acquire(int semid){ |
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struct sembuf sops[2]; |
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sops[0].sem_num = 0; |
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sops[0].sem_op = -1; |
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sops[0].sem_flg = SEM_UNDO; |
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if (semop(semid, sops, 1) == -1) { |
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perror("acquire"); |
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exit(1); |
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} |
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} |
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int release(int semid){ |
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struct sembuf sops[2]; |
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sops[0].sem_num = 0; /* Operate on semaphore 0 */ |
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sops[0].sem_op = 1; /* Wait for value to equal 0 */ |
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sops[0].sem_flg = SEM_UNDO; |
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if (semop(semid, sops, 1) == -1) { |
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perror("release"); |
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exit(1); |
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} |
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} |
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void p(int semid, int i){ |
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int j; |
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acquire(semid); |
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for(j=0; j<10; j++){ |
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printf("%i\n",i); |
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sleep(1); |
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} |
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release(semid); |
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} |
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int main(int argc, char **argv){ |
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key_t key; |
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int semid; |
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int wait_status; |
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union semun { |
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int val; /* Value for SETVAL */ |
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struct semid_ds *buf; /* Buffer for IPC_STAT, IPC_SET */ |
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unsigned short *array; /* Array for GETALL, SETALL */ |
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struct seminfo *__buf; /* Buffer for IPC_INFO |
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(Linux-specific) */ |
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}; |
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int v; |
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union semun su; |
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//key=ftok("l-.l", 0x55); |
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//printf("key=%i\n",key); |
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key=IPC_PRIVATE; |
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semid=semget(key, 1, IPC_CREAT|0666); |
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printf("semid=%i\n",semid); |
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su.val=1; |
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v=semctl(semid, 0, SETVAL, su); |
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if(v==-1){ |
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perror("semctl0"); |
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exit(1); |
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} |
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v=semctl(semid, 0, GETVAL); |
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if(v==-1){ |
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perror("semctl1"); |
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exit(1); |
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} |
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printf("val after set: v=%i\n", v); |
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if(fork()){ |
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p(semid, 1); |
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wait(&wait_status); |
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} else { |
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p(semid, 2); |
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} |
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} |
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</nowiki> |
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