使用共享内存时子进程挂起?
作者:互联网
我正在从一些C代码中得到一些非常奇怪的输出.当然,我是C和Linux开发的新手,因为我的背景是.NET和C#.
无论如何,我都应该在c中编写FAT12实现和命令外壳.每当子进程尝试访问共享内存时,我的外壳就会挂起.事实上,什么都没有发生,这确实很奇怪.谁能帮我调试代码?
谢谢,
这是运行shell的主要循环:
while(strcmp(input, "EXIT") != 0 )
{
scanf("%s", input);
input = String_ToFixedArray(input);
array = StringArray_Create(input, " "); //split the input string into array.
if( array->Items == NULL || array->Size == 0 )
{
input = "CONTINUE";
continue;
}
if( strcmp(String_ToUpper(array->Items[0]), "PBS") == 0)
{
pid_t processId;
if((processId = fork()) < 0 )
{
printf("%s", "Error executing command.");
}
//child process. Nothing happens???????
if( processId == 0 )
{
ExecutePBS();
}
}
else if( strcmp(String_ToUpper(array->Items[0]), "PFE") == 0 )
{
printf("Execute Print Fat Entries (PFE) Command\n");
}
else if( strcmp(String_ToUpper(array->Items[0]), "EXIT") == 0 )
{
printf("Exiting..");
break;
}
else
{
input = "CONTINUE";
}
}
这是一个“驱动程序”功能,将打印引导扇区(PBS)的内容.问题在于,无论何时执行此功能,都不会发生任何事情!
void ExecutePBS(void)
{
int shm_file_id;
char* shm_file;
char* shm_file_ptr;
struct shmid_ds shm_file_buffer;
if( (shm_file_id = shmget(SHM_FILE_NAME_KEY,SHM_FILE_NAME_SIZE, 0666)) < 0)
{
perror("Error locating shared memory segment.");
exit(1);
}
if((shm_file = shmat(shm_file_id, NULL, 0)) == (char *) -1)
{
perror("Error attaching shared memory segment to process' scope.");
exit(1);
}
if(shmctl(shm_file_id, IPC_STAT, &shm_file_buffer) == -1 )
{
perror("Error while attempting to control the shared memory segment used to store the floppy file name for IPC.");
exit(1);
}
sprintf(shm_file_ptr, "%s", shm_file);
if( shmdt(shm_file) == -1)
{
perror("Error releasing shared memory.");
exit(1);
}
FILE* floppyImage = fopen(shm_file_ptr, "r+");
if (floppyImage == NULL)
{
printf("Could not open the floppy drive or image.\n");
exit(1);
}
BootSector* bootSector = BootSector_ReadBootSector(floppyImage);
BootSector_ToString(bootSector);
return;
}
解决方法:
并不是很大的分支……但我的理解是,对于子进程,它返回= 0!对于父进程,它返回= 0 …因此,您应该有两种逻辑,每种情况一种…在客户端调用该方法之后,它也会开始同时在while循环中循环,对吗?还..“什么都没有发生”是什么意思…您是否尝试过放置printfs以增加可见性?
标签:shared-memory,c-3,linux,fork 来源: https://codeday.me/bug/20191102/1993620.html