我可以共享一个文件描述符在Linux上另一个进程或者是他们本地的过程? [英] Can I share a file descriptor to another process on linux or are they local to the process?
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问题描述
说我有2个进程,ProcessA和进程B。如果我执行 INT FD =开(somefile)
在ProcessA,我可以再传给文件描述符的值 FD
结束工控机进程B,并将它操作同一个文件?
Say I have 2 processes, ProcessA and ProcessB. If I perform int fd=open(somefile)
in ProcessA, can I then pass the value of file descriptor fd
over IPC to ProcessB and have it manipulate the same file?
推荐答案
您可以通过一个文件描述符到另一个进程在 Unix域插座。
这里的code通过这样一个文件描述符,从 unix网络编程采取
You can pass a file descriptor to another process over unix domain sockets. Here's the code to pass such a file descriptor, taken from Unix Network Programming
ssize_t
write_fd(int fd, void *ptr, size_t nbytes, int sendfd)
{
struct msghdr msg;
struct iovec iov[1];
#ifdef HAVE_MSGHDR_MSG_CONTROL
union {
struct cmsghdr cm;
char control[CMSG_SPACE(sizeof(int))];
} control_un;
struct cmsghdr *cmptr;
msg.msg_control = control_un.control;
msg.msg_controllen = sizeof(control_un.control);
cmptr = CMSG_FIRSTHDR(&msg);
cmptr->cmsg_len = CMSG_LEN(sizeof(int));
cmptr->cmsg_level = SOL_SOCKET;
cmptr->cmsg_type = SCM_RIGHTS;
*((int *) CMSG_DATA(cmptr)) = sendfd;
#else
msg.msg_accrights = (caddr_t) &sendfd;
msg.msg_accrightslen = sizeof(int);
#endif
msg.msg_name = NULL;
msg.msg_namelen = 0;
iov[0].iov_base = ptr;
iov[0].iov_len = nbytes;
msg.msg_iov = iov;
msg.msg_iovlen = 1;
return(sendmsg(fd, &msg, 0));
}
/* end write_fd */
和这里的code接收文件描述符
And here's the code to receive the file descriptor
ssize_t
read_fd(int fd, void *ptr, size_t nbytes, int *recvfd)
{
struct msghdr msg;
struct iovec iov[1];
ssize_t n;
int newfd;
#ifdef HAVE_MSGHDR_MSG_CONTROL
union {
struct cmsghdr cm;
char control[CMSG_SPACE(sizeof(int))];
} control_un;
struct cmsghdr *cmptr;
msg.msg_control = control_un.control;
msg.msg_controllen = sizeof(control_un.control);
#else
msg.msg_accrights = (caddr_t) &newfd;
msg.msg_accrightslen = sizeof(int);
#endif
msg.msg_name = NULL;
msg.msg_namelen = 0;
iov[0].iov_base = ptr;
iov[0].iov_len = nbytes;
msg.msg_iov = iov;
msg.msg_iovlen = 1;
if ( (n = recvmsg(fd, &msg, 0)) <= 0)
return(n);
#ifdef HAVE_MSGHDR_MSG_CONTROL
if ( (cmptr = CMSG_FIRSTHDR(&msg)) != NULL &&
cmptr->cmsg_len == CMSG_LEN(sizeof(int))) {
if (cmptr->cmsg_level != SOL_SOCKET)
err_quit("control level != SOL_SOCKET");
if (cmptr->cmsg_type != SCM_RIGHTS)
err_quit("control type != SCM_RIGHTS");
*recvfd = *((int *) CMSG_DATA(cmptr));
} else
*recvfd = -1; /* descriptor was not passed */
#else
/* *INDENT-OFF* */
if (msg.msg_accrightslen == sizeof(int))
*recvfd = newfd;
else
*recvfd = -1; /* descriptor was not passed */
/* *INDENT-ON* */
#endif
return(n);
}
/* end read_fd */
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