使用IPC_PRIVATE信号量简单的例子
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Linux 信号量的API都定义在sys/sem.h头文件中,主要包含3个系统调用:semget、semop、semctl。
附上代码:
#include <sys/sem.h> #include <stdio.h> #include <stdlib.h> #include <unistd.h> #include <sys/wait.h> union semun { int val; struct semid_ds* buf; unsigned short int* array; struct seminfo* __buf; }; void pv( int sem_id, int op ) { struct sembuf sem_b; sem_b.sem_num = 0; sem_b.sem_op = op; sem_b.sem_flg = SEM_UNDO; semop( sem_id, &sem_b, 1 ); } int main( int argc, char* argv[] ) { int sem_id = semget( IPC_PRIVATE, 1, 0666 ); union semun sem_un; sem_un.val = 1; semctl( sem_id, 0, SETVAL, sem_un ); pid_t id = fork(); if( id < 0 ) { return 1; } else if( id == 0 ) { printf( "child try to get binary sem\\n" ); pv( sem_id, -1 ); printf( "child get the sem and would release it after 5 seconds\\n" ); sleep( 5 ); pv( sem_id, 1 ); exit( 0 ); } else { printf( "parent try to get binary sem\\n" ); pv( sem_id, -1 ); printf( "parent get the sem and would release it after 5 seconds\\n" ); sleep( 5 ); pv( sem_id, 1 ); } waitpid( id, NULL, 0 ); semctl( sem_id, 0, IPC_RMID, sem_un ); return 0; }
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