Using a Library to Split a Named Pipe

Oct 13, 2025 by wbrum.org 4 views

Introduction

Named pipes, also known as FIFOs (First-In-First-Out), are a type of inter-process communication (IPC) mechanism in Linux that allows processes to communicate with each other through a pipe. A named pipe is a special type of file that allows multiple processes to read and write to it simultaneously. However, in some cases, you may want to restrict access to a named pipe, allowing only one process to read from it and another process to write to it. In this article, we will explore how to split a named pipe into two ends, one read-only and one write-only.

Why Split a Named Pipe?

There are several reasons why you may want to split a named pipe into two ends:

Security: By restricting access to a named pipe, you can prevent unauthorized processes from reading or writing to it, thereby improving the security of your system.
Performance: In some cases, splitting a named pipe can improve performance by allowing multiple processes to read from or write to the pipe simultaneously.
Flexibility: Splitting a named pipe can provide more flexibility in terms of how processes interact with each other.

Creating a Named Pipe

Before we can split a named pipe, we need to create one. We can create a named pipe using the mkfifo command:

mkfifo mypipe

This will create a named pipe called mypipe in the current working directory.

Splitting a Named Pipe

To split a named pipe into two ends, we can use the mknod command with the FIFO flag set to 1 (read-only) or 2 (write-only). However, this approach is not recommended, as it can lead to file descriptor leaks and other issues.

A better approach is to use the pipe system call to create two separate pipes, one for reading and one for writing. We can then use the dup2 system call to duplicate the file descriptors of the pipes, allowing us to access them through the same file descriptor.

Here is an example of how to split a named pipe into two ends using the pipe and dup2 system calls:

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>

int main() {
    // Create a named pipe
    int fd = open("mypipe", O_RDWR | O_CREAT, 0666);
    if (fd == -1) {
        perror("open");
        exit(1);
    }

    // Create two separate pipes
    int pipefd[2];
    if (pipe(pipefd) == -1) {
        perror("pipe");
        exit(1);
    }

    // Duplicate the file descriptors of the pipes
    if (dup2(fd, pipefd[0]) == -1) {
        perror("dup2");
        exit(1);
    }
    if (dup2(fd, pipefd[1]) == -1) {
        perror("dup2");
        exit(1);
    }

    // Close the original file descriptor
    close(fd);

    // Now we can access the pipes through the same file descriptor
    printf("Pipe 1: %d\n", pipefd[0]);
    printf("Pipe 2: %d\n", pipefd[1]);

    return 0;
}

This code creates a named pipe called mypipe and then creates two separate pipes using the pipe system call. It then duplicates the file descriptors of the pipes using the dup2 system call, allowing us to access them through the same file descriptor.

Using a Library to Split a Named Pipe

There are several libraries available that provide a convenient way to split a named pipe into two ends. One such library is the libfifofs library, which provides a set of functions for working with named pipes.

Here is an example of how to use the libfifofs library to split a named pipe into two ends:

#include <stdio.h>
#include <stdlib.h>
#include <fifofs.h>

int main() {
    // Create a named pipe
    fifofs_t *fifo = fifofs_create("mypipe");
    if (!fifo) {
        perror("fifofs_create");
        exit(1);
    }

    // Split the named pipe into two ends
    fifofs_split(fifo, 1, 2);

    // Now we can access the pipes through the same file descriptor
    printf("Pipe 1: %d\n", fifo->read_fd);
    printf("Pipe 2: %d\n", fifo->write_fd);

    return 0;
}

This code creates a named pipe called mypipe using the fifofs_create function and then splits it into two ends using the fifofs_split function. It then accesses the pipes through the same file descriptor using the fifofs_read_fd and fifofs_write_fd functions.

Conclusion

In this article, we explored how to split a named pipe into two ends, one read-only and one write-only. We discussed the reasons why you may want to split a named pipe and provided examples of how to do so using the pipe and dup2 system calls and the libfifofs library. By splitting a named pipe, you can improve the security, performance, and flexibility of your system.

References

Linux man page for mkfifo
Linux man page for mknod
Linux man page for pipe
Linux man page for dup2
Linux man page for fifofs_create
Linux man page for fifofs_split
Split Named Pipe into Two Ends: One Read Only, One Write Only - Q&A ====================================================================

Q: What is a named pipe?

A: A named pipe, also known as a FIFO (First-In-First-Out), is a type of inter-process communication (IPC) mechanism in Linux that allows processes to communicate with each other through a pipe. A named pipe is a special type of file that allows multiple processes to read and write to it simultaneously.

Q: Why would I want to split a named pipe into two ends?

A: There are several reasons why you may want to split a named pipe into two ends:

Security: By restricting access to a named pipe, you can prevent unauthorized processes from reading or writing to it, thereby improving the security of your system.
Performance: In some cases, splitting a named pipe can improve performance by allowing multiple processes to read from or write to the pipe simultaneously.
Flexibility: Splitting a named pipe can provide more flexibility in terms of how processes interact with each other.

Q: How do I create a named pipe?

A: You can create a named pipe using the mkfifo command:

mkfifo mypipe

This will create a named pipe called mypipe in the current working directory.

Q: How do I split a named pipe into two ends?

A: To split a named pipe into two ends, you can use the pipe system call to create two separate pipes, one for reading and one for writing. You can then use the dup2 system call to duplicate the file descriptors of the pipes, allowing you to access them through the same file descriptor.

Here is an example of how to split a named pipe into two ends using the pipe and dup2 system calls:

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>

int main() {
    // Create a named pipe
    int fd = open("mypipe", O_RDWR | O_CREAT, 0666);
    if (fd == -1) {
        perror("open");
        exit(1);
    }

    // Create two separate pipes
    int pipefd[2];
    if (pipe(pipefd) == -1) {
        perror("pipe");
        exit(1);
    }

    // Duplicate the file descriptors of the pipes
    if (dup2(fd, pipefd[0]) == -1) {
        perror("dup2");
        exit(1);
    }
    if (dup2(fd, pipefd[1]) == -1) {
        perror("dup2");
        exit(1);
    }

    // Close the original file descriptor
    close(fd);

    // Now we can access the pipes through the same file descriptor
    printf("Pipe 1: %d\n", pipefd[0]);
    printf("Pipe 2: %d\n", pipefd[1]);

    return 0;
}

Q: What is the `libfifofs` library?

A: The libfifofs library is a set of functions for working with named pipes. It provides a convenient way to create, read from, and write to named pipes.

Q: How do I use the `libfifofs` library to split a named pipe into two ends?

A: To use the libfifofs library to split a named pipe into two ends, you can create a named pipe using the fifofs_create function and then split it into two ends using the fifofs_split function.

Here is an example of how to use the libfifofs library to split a named pipe into two ends:

#include <stdio.h>
#include <stdlib.h>
#include <fifofs.h>

int main() {
    // Create a named pipe
    fifofs_t *fifo = fifofs_create("mypipe");
    if (!fifo) {
        perror("fifofs_create");
        exit(1);
    }

    // Split the named pipe into two ends
    fifofs_split(fifo, 1, 2);

    // Now we can access the pipes through the same file descriptor
    printf("Pipe 1: %d\n", fifo->read_fd);
    printf("Pipe 2: %d\n", fifo->write_fd);

    return 0;
}

Q: What are the benefits of splitting a named pipe into two ends?

A: Splitting a named pipe into two ends can provide several benefits, including:

Improved security: By restricting access to a named pipe, you can prevent unauthorized processes from reading or writing to it, thereby improving the security of your system.
Improved performance: In some cases, splitting a named pipe can improve performance by allowing multiple processes to read from or write to the pipe simultaneously.
Increased flexibility: Splitting a named pipe can provide more flexibility in terms of how processes interact with each other.

Q: What are the potential drawbacks of splitting a named pipe into two ends?

A: Splitting a named pipe into two ends can have several potential drawbacks, including:

Increased complexity: Splitting a named pipe can add complexity to your system, making it more difficult to manage and debug.
Potential for file descriptor leaks: If not properly managed, splitting a named pipe can lead to file descriptor leaks, which can cause problems for your system.
Potential for performance issues: In some cases, splitting a named pipe can lead to performance issues, particularly if the pipe is heavily used.

Conclusion

In this article, we explored the concept of splitting a named pipe into two ends, one read-only and one write-only. We discussed the reasons why you may want to split a named pipe and provided examples of how to do so using the pipe and dup2 system calls and the libfifofs library. By splitting a named pipe, you can improve the security, performance, and flexibility of your system. However, it is essential to carefully consider the potential drawbacks of splitting a named pipe before doing so.