我遇到了一个问题,当我使用a.out
命令来运行我的./a.out
文件。我正在分割代码错误号11.试图访问共享内存时,我得到一个分段错误。我用memcpy
将数据粘贴到共享内存中。它是分段故障11。
我是否正确地访问内存?
#include<stdio.h>
#include<sys/types.h>
#include<sys/shm.h>
#include<sys/ipc.h>
#include<unistd.h>
#include<time.h>
int main(){
pid_t childPid;
childPid = fork();
char *shm;
if(childPid == 0){
char *args[] ={"ls","-l",NULL};
int shmid;
int shsize = 100;
key_t key;
char *s;
key = 9876;
shmid = shmget(key,shsize, IPC_CREAT | 0666);
if(shmid < 0){
printf("error getting shmid");
exit(1);
}
shm = shmat(shmid,NULL,0);
if(shm == (char *) -1){
printf("error getting shared memory");
exit(1);
}
time_t startTime;
gettimeofday(&startTime,0);
memcpy(shm,&startTime,sizeof(startTime));
time_t endTime;
execvp(args[0],args);
printf("successfuly created child proceess");
exit(0);
}
else if (childPid <0){
printf("unsuccessfuly created child proccess");
else{
int returnStatus;
waitpid(childPid,&returnStatus,0);
if(returnStatus == 0){
printf("The child terminated normally");
printf("%s",*shm);
}
if(returnStatus == 1){
printf("The child terminated with error");
}
}
}
}
在
time_t startTime;
gettimeofday(&startTime,0);
gettimeofday的第一个参数必须是一个struct timeval *
不是time_t *
所以
struct timeval startTime;
gettimeofday(&startTime,0);
在
char *shm;
...
printf("%s",*shm);
你一定不要提领SHM,因为目前它的第一个字符的ASCII码作为字符串的地址,必须是
char *shm;
...
printf("%s",shm);
后
else if (childPid <0){
printf("unsuccessfuly created child proccess");
一个}
缺失
我鼓励你编译要求编译器生成的警告,用gcc使用的选项-pedantic -Wall