#include <stdio.h>#include <sys/types.h>#include <sys/ipc.h>#include <sys/shm.h>extern int etext,edata,end;int main(int argc,char* argv[]){	int shmid;	int proj_id;	key_t key;	int shm_size;	char* shm_addr,*addr;	pid_t pid;		if(argc!=3){		printf("Usage: %s shared_memory_size info\n",argv[0]);		return 1;	}	shm_size=atoi(argv[1]);	proj_id=2;        key=ftok("/home/program",proj_id);        if(key==-1){                perror("cannot generate the IPC key");                return 1;        }	shmid=shmget(key,shm_size,IPC_CREAT | 0660);	if(shmid==-1){		perror("cannot create a shared memory segment");		return 1;	}	addr=(char*)shmat(shmid,NULL,0);	shm_addr=addr;	if(shm_addr==(char*)(-1)){		perror("cannot attach the shared memory to process");		return 1;	}	printf("====address information===\n");	printf("etext address: %x\n",&etext);	printf("edata address: %x\n",&edata);	printf("end address: %x\n",&end);	printf("shared memory segment address: %x\n",shm_addr);	printf("==========================\n");		strcpy(shm_addr,argv[2]);	printf("the input string is : %s\n",argv[2]);		printf("before fork,in shared memory segment the string is: %s\n",shm_addr);	pid=fork();	if(pid==-1){		perror("cannot create new process");		return 1;	}else if(pid==0){		printf("in child process, the string is %s \n",shm_addr);		printf("modify the content in shared memory\n");				*shm_addr +=1;					_exit(0);				}else{		wait(NULL);		printf("after fork, in shared memory segment the string is %s\n",shm_addr);		if(shmdt(shm_addr)==-1){			perror("cannot release the memory");			return 1;		}				if(shmctl(shmid,IPC_RMID,NULL)==-1){			perror("cannot delete existing shared memory segment");			return 1;		}	}	return 0;}