How to Use the Command 'mkfifo' (with Examples)
The mkfifo command is a tool used to create FIFOs, also known as named pipes, which allow for more complex inter-process communication by establishing a pipe that multiple processes can attach to in the filesystem. These named pipes differ from anonymous pipes by providing a pathway for communication that persists as a file on the system and can be accessed or shared across processes, even if they are not directly related. This command finds its utility in various scripting and system administration tasks where inter-process communication is needed without reliance on direct pipes.
Use Case 1: Create a Named Pipe at a Given Path
Code:
mkfifo path/to/pipe
Motivation:
Creating a named pipe using this command is a foundational task when setting up a communication channel between different processes. This setup allows for data flow management between separate applications or scripts, which can be particularly useful in complex systems or networks that require asynchronous processing. Named pipes provide a reliable and an easy-to-implement approach without needing to establish new protocols or networks.
Explanation:
mkfifo: This command initializes the creation process of a named pipe.path/to/pipe: This argument specifies the file path where the named pipe will be created. It essentially refers to where the FIFO special file will reside, acting as the terminal for communication.
Example Output:
Upon running the command, you won’t see any direct output in the shell. Instead, navigating to the specified directory with ls shows the named pipe, marked with a special designation to indicate it is a FIFO.
Use Case 2: Send Data Through a Named Pipe and Send the Command to the Background
Code:
echo "Hello World" > path/to/pipe &
Motivation:
This command sends a specified message or data through a named pipe, allowing the receiving process to pick up this data asynchronously. Sending the command to the background (using &) ensures that the running shell is not blocked, enabling further commands to be executed simultaneously. This is essential for scenarios where you might want to send data to multiple pipes or continue processing without waiting for the pipe operation to conclude.
Explanation:
echo "Hello World": This command outputs the string “Hello World”.>: The redirection operator sends the output of the echo command to the specified named pipe.path/to/pipe: This path specifies where the data should be sent, indicating the named pipe’s location.&: Running the command in the background means it executes independently of the shell’s job control, allowing for parallel operations.
Example Output:
This operation does not produce a visible output in the shell. However, any process reading from path/to/pipe will receive the "Hello World" string as input.
Use Case 3: Receive Data Through a Named Pipe
Code:
cat path/to/pipe
Motivation:
By reading data from a named pipe, this use case demonstrates how data written to a pipe can be consumed by another process. It’s a fundamental step in bi-directional communication between applications or scripts, enabling inter-process messaging in real-time. This scenario is invaluable in dynamically receiving incoming data without storing it in intermediary formats or files.
Explanation:
cat: This command is typically used to concatenate and display content of files.path/to/pipe: In this context,catreads and displays any data that is being pushed to the named pipe, showing its contents directly in the command line.
Example Output:
When data is sent through the pipe, its content will be output in real-time to the terminal running the cat command. If "Hello World" was piped in the previous example, this terminal will display Hello World.
Use Case 4: Share Your Terminal Session in Real-Time
Code:
mkfifo path/to/pipe; script -f path/to/pipe
Motivation:
Sharing a terminal session in real-time via named pipes is particularly useful for collaborative troubleshooting or teaching scenarios. This setup allows another user or process to view everything happening in your terminal live as it happens. It creates an interactive log that can be followed without physically being present at the terminal, enhancing remote collaboration and ease of monitoring.
Explanation:
mkfifo path/to/pipe: Creates the named pipe as described previously.script: This command records a session of terminal activity and is used here to log the session.-f: Means to flush the output to the pipe as it happens, allowing any connected reader to receive updates in real-time.path/to/pipe: Specifies the FIFO to use for feeding the terminal session activities.
Example Output:
Like previous examples, this doesn’t display an output itself, but once setup, any connected readers monitoring path/to/pipe will see real-time updates of terminal activities.
Conclusion:
The mkfifo command offers versatile means of setting up inter-process communication through named pipes. Use cases vary from facilitating simple message passing between processes to sharing terminal sessions for collaborative efforts, each building on the concept of seamless data flow without traditional file-based intermediary steps. By integrating mkfifo into your workflow, you can enable more dynamic and complex interactions between applications and users, allowing for increased flexibility and operational efficiency.
