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RPC stands for remote procedure call.  It is generally one userspace processes
communicating with another userspace process.  For example, a user may use
emacs to open a text file for editing.  On the Hurd, glibc turns the C function
call into appropriate RPC calls to ext2fs. It is important to remember that
gnumach's IPC facilitates this communication between emacs and ext2fs (with
the gnumach mach_msg () syscall: one to send the message and one to receive
the reply).

It is also important to distinguish an RPC from a [[system call|system_call]].
A system call, happens when a userspace process requests something of the kernel.
An RPC is generally one userspace process requesting something from another
userspace process.




# See Also

  * [[Mach RPC|microkernel/mach/rpc]]s

  * [[RPC usage in the Hurd|hurd/rpc]]

  * the [[Hurd's rpctrace|hurd/debugging/rpctrace]]