Named Pipes (FIFO Files)¶

Table of Contents¶

Description of Named Pipes
Named Pipe Usage
Examples of Using Named Pipes (FIFO Files)
- Streaming Log Files
- Transcoding a Video Stream
Breakdown of Named Pipes

Description of Named Pipes¶

What is a Named Pipe?¶

A named pipe is a special kind of file that exists as a name in the
filesystem but behaves like a pipe.

It provides a FIFO communication channel between two or more processes.

How it Works¶

Data written to a named pipe by one process can be read by another
process in the order it was written, hence "first in, first out."

Unlike regular files, named pipes do not store data on the filesystem.

Uses¶

Named pipes are useful for inter-process communication, especially when
you want to transfer data between processes without writing to disk.

They can be used for logging, streaming data, message passing, and more.

Benefits¶

Named pipes provide a simple and effective way to achieve real-time data
processing and communication between processes.

This can minimize the need for temporary files and potentially reducing I/O overhead.

Named Pipe Usage¶

Named Pipe Creation¶

A named pipe is created using mkfifo.

mkfifo my_pipe

This acts as a temporary file that you can use to capture the output of a process.

Relevant Conditional Statements¶

-p file returns true if file exists and is a named pipe (FIFO).

Capturing the Output of a Background Process¶

See background processes.¶

This script captures the output of a background process and waits until
the program is ready to accept connections.

mkfifo my_pipe  
(./my_program > my_pipe 2>&1 &)  # & runs the program in the background  
printf "Waiting for program to be ready...\n"  
while IFS= read -r line; do  
    if printf "%s\n" "$line" | grep -i 'ready to accept connections'; then  
        printf "Program is ready to accept connections.\n"  
        break  
    fi  
done < my_pipe  
rm my_pipe  # Clean up the file

Examples of Using Named Pipes (FIFO Files)¶

Named pipes, or FIFO (First In, First Out) files, are a type
of file that acts as a pipe between two or more processes.

Data written to a named pipe by one process can be read by another, facilitating inter-process communication.

Streaming Log Files¶

You can stream log output from one process to another for real-time processing or monitoring.

mkfifo /tmp/logpipe  
tail -f /var/log/myapp.log > /tmp/logpipe &  
grep "ERROR" < /tmp/logpipe > /tmp/error_logs

This setup allows you to filter for error messages in real-time
from an application's log file and save them to a separate file.

Transcoding a Video Stream¶

Use ffmpeg to transcode video and stream the output directly
to a player like vlc without intermediate files.

mkfifo /tmp/videostream  
ffmpeg -i input.mp4 -f mpegts /tmp/videostream &  
vlc /tmp/videostream