[英]Pass File Descriptor - Execve (typecast)
I am wondering how I can pass a file descriptor through the execve()
command and then access it on the other side. 我想知道如何通过
execve()
命令传递文件描述符,然后在另一端访问它。 I know that I can use dup2
to redirect the file-descriptor but I cannot do that. 我知道我可以使用
dup2
重定向文件描述符,但我不能这样做。 I am required to actually pass the file descriptor to the child and use it in the child. 我需要实际将文件描述符传递给子进程并在子进程中使用它。
What I have done so far: 到目前为止我做了什么:
Parent makes pipe
+ args like the following: Parent生成
pipe
+ args,如下所示:
int pfd[2];
if(pipe(pfd) == -1)
exitWithError("PIPE FAILED", 1);
char *args_1[] = {"reader", argv[1], (char*) pfd, (char *) 0};
Then the child calls execve
after fork()
like the following: 然后孩子在
fork()
之后调用execve
,如下所示:
close(pfd[1]);
execve("./reader", args_1, NULL);
Then, in the reader program I try to access pipe descriptor that was passed: 然后,在读者程序中,我尝试访问传递的管道描述符:
int main(int argc, char* argv[]){
...
write(argv[2][1], buf, read_test);
argv[2]
should be referencing the pipe descriptor, then the argv[1]
should go to the write end of the pipe. argv[2]
应该引用管道描述符,然后argv[1]
应该转到管道的写端。 I am almost positive that I need to do some type-casting differently here, but everything I try doesn't quite work out. 我几乎肯定我需要在这里做一些不同的类型转换,但我尝试的一切都不太合适。
NOTE : I have a working version of this program using dup2
to redirect to stdin
and stdout
for the children, but I have to actually pass the pipe descriptor to a child as per instructions of the project. 注意 :我有一个这个程序的工作版本,使用
dup2
重定向到孩子们的stdin
和stdout
,但是我必须按照项目的指示将管道描述符传递给子节点。
Any help is appreciated. 任何帮助表示赞赏。
Simply casting the file descriptor to a char*
isn't a good idea. 简单地将文件描述符转换为
char*
并不是一个好主意。 It could cause data loss if the OS chooses to copy the strings and stops at the 0 bytes, so the data isn't entirely copied. 如果操作系统选择复制字符串并停止在0字节,则可能导致数据丢失,因此数据不会完全复制。 It would be safer to create a string containing the file descriptor.
创建包含文件描述符的字符串会更安全。
int pfd[2];
if(pipe(pfd) == -1)
exitWithError("PIPE FAILED", 1);
char string1[12]; // A 32 bit number can't take more than 11 characters, + a terminating 0
snprintf(string1,12,"%i",pfd[1]); // Copy the file descriptor into a string
char *args_1[] = {"reader", argv[1], &string1[0], (char *) 0};
The reader program then uses atoi
to convert this back into an int. 读者程序然后使用
atoi
将其转换回int。
int fd = atoi(argv[2]);
write(fd,buf,read_test);
If you really want to use a cast, then you need to cast argv[2]
as int*
in your reader. 如果你真的想使用强制转换,那么你需要在你的读者中将
argv[2]
为int*
。
write(((int*)argv[2])[1],buf,read_test);
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