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  1. /*
  2.  * shared memory - header file
  3.  *
  4. */
  5.  
  6. #include <stdio.h>
  7. #include <sys/types.h>
  8. #include <sys/ipc.h>
  9. #include <sys/shm.h>
  10. #include <errno.h>
  11. #include <semaphore.h>
  12.  
  13. #define SHMKEY          0x123
  14. #define PERMS           0666
  15.  
  16. extern int errno;
  17.  
  18. typedef struct 
  19. {
  20.   sem_t sem1; 
  21.   sem_t sem2;
  22. }CFG_SHM;
  23.  
  24.  
  25. #include <stdio.h>
  26. #include <pthread.h>
  27. #include <semaphore.h>
  28. #include <unistd.h>
  29.  
  30.  
  31. int main(void)
  32. {
  33.    int childpid;
  34.    int val;
  35.    CFG_SHM *cfgshmPtr,cfgdata;                                
  36.   int shmid;
  37.  
  38. 	shmid = shmget(SHMKEY,sizeof(CFG_SHM),IPC_CREAT|PERMS);   //create the shared
  39. 	if(shmid < 0)                                             //memory segment
  40. 	{
  41. 		printf("Error in getting shared memory, %s",strerror(errno));
  42. 		exit(0);
  43. 	}
  44. 	cfgshmPtr = (CFG_SHM *) shmat(shmid,0,0);      
  45. 	if(cfgshmPtr == (CFG_SHM *) 0)                
  46. 	{
  47. 		printf("Error in attaching shared memory, %s",strerror(errno));
  48. 		exit(0);
  49. 	}
  50.   memcpy((void *)&cfgdata,(void *)cfgshmPtr,sizeof(CFG_SHM));
  51.  
  52.  
  53. 	sem_init(&(cfgshmPtr->sem1), 0, 1);
  54.     sem_init(&(cfgshmPtr->sem2), 0, 0);
  55. 	childpid=fork();
  56. 	if(childpid < 0)
  57. 	{
  58. 		printf("Fork failed\n");
  59. 		exit(1);
  60. 	}
  61. 	if (childpid==0)
  62. 	{
  63. 		int OddNum=1;
  64. 		printf("The number is 1 Odd \n");
  65. 		while (OddNum < 9)
  66. 		{
  67. 			shmid = shmget(SHMKEY,sizeof(CFG_SHM),IPC_CREAT|PERMS);   //create the shared
  68. 			if(shmid < 0)                                             //memory segment
  69. 			{
  70. 				printf("Error in getting shared memory, %s",strerror(errno));
  71. 				exit(0);
  72. 			}
  73.  		    cfgshmPtr = (CFG_SHM *) shmat(shmid,0,0);     //attach it to the 
  74. 		    if(cfgshmPtr == (CFG_SHM *) 0)                //process
  75. 		    {
  76. 				printf("Error in attaching shared memory, %s",strerror(errno));
  77. 				exit(0);
  78. 		    }
  79. 		/*
  80. 			sem_getvalue(&(cfgshmPtr->sem1), &val);
  81. 			printf("Child :The sem1 value is %d \n", val);
  82. 		    sem_getvalue(&(cfgshmPtr->sem2), &val);
  83. 			printf("Child :The sem2 value is %d \n", val);
  84. 	     */
  85. 			sem_wait(&(cfgshmPtr->sem2));
  86. 			OddNum=OddNum+2;
  87. 			printf("The number is %d Odd \n", OddNum);
  88. 			sem_post(&(cfgshmPtr->sem1));
  89.     		if(shmdt(cfgshmPtr) < 0)                 //detach the shared memory segment 
  90.             printf("Error in detaching shared memory segment, %s\n",strerror(errno));
  91. 		}
  92. 	}
  93. 	else
  94. 	{
  95. 		int EvenNum=0;
  96. 		while (EvenNum < 10)
  97. 		{   
  98. 			shmid = shmget(SHMKEY,sizeof(CFG_SHM),IPC_CREAT|PERMS);   //create the shared
  99. 			if(shmid < 0)                                             //memory segment
  100. 			{
  101. 				printf("Error in getting shared memory, %s",strerror(errno));
  102. 				exit(0);
  103. 			}
  104.  		    cfgshmPtr = (CFG_SHM *) shmat(shmid,0,0);     //attach it to the 
  105. 		    if(cfgshmPtr == (CFG_SHM *) 0)                //process
  106. 		    {
  107. 				printf("Error in attaching shared memory, %s",strerror(errno));
  108. 				exit(0);
  109. 		    }
  110. 		/*
  111. 			sem_getvalue(&(cfgshmPtr->sem1), &val);
  112. 			printf("Parent :The sem1 value is %d \n", val);
  113. 		    sem_getvalue(&(cfgshmPtr->sem2), &val);
  114. 			printf("Parent :The sem2 value is %d \n", val);
  115. 	    */
  116. 			sem_wait(&(cfgshmPtr->sem1));
  117. 			EvenNum=EvenNum+2;
  118. 			printf("The number is %d Even \n", EvenNum);
  119. 			sem_post(&(cfgshmPtr->sem2));
  120. 			if(shmdt(cfgshmPtr) < 0)                 //detach the shared memory segment 
  121.             printf("Error in detaching shared memory segment, %s\n",strerror(errno));
  122. 		}
  123. 		  if(shmctl(shmid,IPC_RMID,0) < 0)           //remove the shared memory segment
  124. 			 printf("Error in removing shared memory segment, %s\n",strerror(errno));
  125. 		  else
  126. 			printf("Shared memory removed successfully\n");
  127.  
  128. 	}
  129. }
  130.  
  131.  
  132.  
  133.  
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https://ideone.com/ZJkTKS
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Text (text 6.10)
created:
7 years ago
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