Pipes

Linux splice Makes the Pipe a Kernel Data-Transfer Boundary

splice() can transfer bytes between two file descriptors without first copying the payload into a userspace buffer, but the interface requires at least one endpoint to be a pipe. That requirement makes the pipe more than an incidental transport. It is the kernel-visible buffer boundary around which the operation’s offset, blocking, capacity, and partial-progress semantics are defined. This differs from a conventional read() followed by write(). In that sequence, userspace owns an intermediate byte array and can inspect or modify it. With splice(), the payload can remain in kernel-managed storage while the process coordinates movement between endpoints.