s6-portable-utils
Software
skarnet.org

The seekablepipe program

seekablepipe turns the reading end of a pipe into a seekable file descriptor, using a temporary file.

Interface 

     writer | seekablepipe tmpfile reader [ args... ]

seekablepipe writes writer's output to tmpfile, which is unlinked as soon as it is created. Then it execs into reader, reading from a file descriptor on tmpfile.