Named Pipe - in Unix

In Unix

Instead of a conventional, unnamed, shell pipeline, a named pipeline makes use of the filesystem. It is explicitly created using mkfifo or mknod, and two separate processes can access the pipe by name — one process can open it as a reader, and the other as a writer.

For example, one can create a pipe and set up gzip to compress things piped to it:

mkfifo my_pipe gzip -9 -c < my_pipe > out.gz &

In a separate process shell, independently, one could send the data to be compressed:

cat file > my_pipe

The named pipe can be deleted just like any file:

rm my_pipe

A named pipe can be used to transfer information from one application to another without the use of an intermediate temporary file. For example you can pipe the output of gzip into a named pipe like so:

mkfifo --mode=0666 /tmp/namedPipe gzip --stdout -d file.gz > /tmp/namedPipe

Then load the uncompressed data into a MySQL table like so:

LOAD DATA INFILE '/tmp/namedPipe' INTO TABLE tableName;

Without this named pipe one would need to write out the entire uncompressed version of file.gz before loading it into MySQL. Writing the temporary file is both time consuming and results in more I/O and less free space on the hard drive.

PostgreSQL's command line terminal, psql, also supports loading data from named pipes.