begriffs / ringfifo

Nonblocking multi-use named pipes

Nonblocking multi-use named pipes

Ringfifo manages two named pipes to create a virtual fifo. As long as the program is running, writers are never blocked, and readers never get an EOF.

# create foo.in, foo.out and wait for data
$ ringfifo foo &

# echo returns right away
$ echo hi > foo.in

# empties buffer, waits for more
$ cat foo.out
hi

In that example, you can pipe more data to foo.in and cat will continue to print it. If you terminate cat, then ringfifo will again queue incoming lines for later.

The program has a configurable internal line limit, at which point it'll drop old lines from the buffer to make room for new lines.

Usage

ringfifo fifo-name [max-lines]

• fifo-name base name of the virtual fifo. Creates named pipes fifo-name.in and fifo-name.out.
• max-lines line limit of the internal ring buffer. Default 8192.

Each buffered line is currently limited to BUFSIZ characters. I haven't taken the time to make that configurable, but it's an easy change.

Building

Requires POSIX and libderp 0.1.0. Install libderp, and run make. The library will be statically linked into the executable.