Using the `mkfifo` command (with examples)
1: Create a named pipe at a given path
Code:
mkfifo path/to/pipe
Motivation:
Creating a named pipe can be useful in various scenarios where interprocess communication is required. By using mkfifo, we can create a named pipe at a specific path to facilitate communication between different processes.
Explanation:
The mkfifo command is used to create a named pipe, also known as a FIFO (First-In-First-Out) file. It creates a special type of file that provides a channel for communication between processes. The path/to/pipe argument specifies the location where the named pipe should be created.
Example Output:
Running the command mkfifo /tmp/my_pipe will create a named pipe file named “my_pipe” in the “/tmp” directory.
2: More Information
Code:
mkfifo --help
Motivation:
To understand the various options and functionalities offered by the mkfifo command, it is helpful to consult the command’s help documentation. This can provide additional information on the available arguments and how to use them effectively.
Explanation:
When the --help option is passed to the mkfifo command, it displays a help message that includes a brief description of the command, its usage syntax, and a list of available options with their respective explanations.
Example Output:
Executing mkfifo --help will print a help message that provides an overview of the mkfifo command and its usage, along with a list of available options and their respective descriptions.
3: Check the status of a named pipe file
Code:
ls -l path/to/pipe
Motivation:
Sometimes it is necessary to check the status or properties of a named pipe file. By using the ls command with the -l option, we can retrieve detailed information about the named pipe file, including its permissions, owner, group, size, and modification timestamp.
Explanation:
Executing ls -l path/to/pipe retrieves the detailed information about the named pipe file present at the specified path. The -l option is used to display the long format listing of the file, which provides comprehensive information about the file.
Example Output:
Running ls -l /tmp/my_pipe will display detailed information about the named pipe file “my_pipe” located in the “/tmp” directory, including its permissions, owner, group, size, and modification timestamp.
4: Remove a named pipe file
Code:
rm path/to/pipe
Motivation:
There may be situations where a named pipe file is no longer needed and should be removed to free up system resources. The rm command, when used with the appropriate path, can be used to delete the specified named pipe file.
Explanation:
The rm command is commonly used to remove files in Unix-like systems. When invoked with the path to a named pipe file, it deletes the specified file from the filesystem, assuming the user has appropriate permissions.
Example Output:
Executing rm /tmp/my_pipe will remove the named pipe file “my_pipe” located in the “/tmp” directory. If successful, there will be no output or confirmation message displayed.
5: Retrieve the process ID of a background process
Code:
mkfifo /tmp/my_pipe
cat > /tmp/my_pipe &
echo $!
Motivation:
In scenarios where a named pipe is used to facilitate communication between processes running in the background, it can be convenient to retrieve the process ID (PID) of a background process. This allows us to interact with or manage the running process if needed.
Explanation:
The command echo $! prints the PID of the most recently executed background process in the current shell session. By running mkfifo to create a named pipe, followed by executing a process (in this case, cat) that writes to the named pipe in the background using the & symbol, we can use echo $! to obtain the PID of the background process that writes to the named pipe.
Example Output:
Executing the provided code will create a named pipe file, start a background process that writes to the named pipe using cat, and then print the PID of the background process. The output will display the PID of the cat process running in the background.
Conclusion
In this article, we explored various use cases of the mkfifo command by providing code examples and explanations for each case. From creating named pipes to checking their status, removing them, and retrieving the PID of background processes, the mkfifo command offers flexibility for interprocess communication and management.
