| .TH SENDFD 3 | |
| .SH NAME | |
| sendfd, recvfd \- pass file descriptors along Unix domain sockets | |
| .SH SYNOPSIS | |
| .B | |
| #include <u.h> | |
| .PP | |
| .B | |
| #include <libc.h> | |
| .PP | |
| .B | |
| int sendfd(int socket, int fd) | |
| .PP | |
| .B | |
| int recvfd(int socket) | |
| .SH DESCRIPTION | |
| .I Recvfd | |
| and | |
| .I sendfd | |
| can be used to pass an open file descriptor over | |
| a Unix domain socket from one process to another. | |
| Since | |
| .IR pipe (3) | |
| is implemented with | |
| .IR socketpair (2) | |
| instead of | |
| .IR pipe (2), | |
| .I socket | |
| can be a file descriptor obtained from | |
| .IR pipe (3). | |
| .PP | |
| .I Sendfd | |
| sends the file descriptor | |
| .I fd | |
| along the socket to a process calling | |
| .I recvfd | |
| on the other end. | |
| .PP | |
| It is assumed that the two sides have coordinated | |
| and agreed to transfer a file descriptor already, so | |
| that the | |
| .I sendfd | |
| is met with a | |
| .I recvfd | |
| instead of an ordinary | |
| .IR read . | |
| .PP | |
| The file descriptor number may change on its way | |
| between processes, but the kernel structure it represents | |
| will not. | |
| .SH SOURCE | |
| .B \*9/src/lib9/sendfd.c | |
| .SH SEE ALSO | |
| .IR socketpair (2), | |
| .I sendmsg | |
| in | |
| .IR send (2) |