SHM Modbus - Shared Memory Writer

SHM Modbus > Modbus Tools > write

The write-shm application writes the content from its standard input to a named shared memory. It provides options to specify the shared memory name and optionally protect it with an existing named semaphore against simultaneous access. Additionally, options are available to invert input bits, repeat input if the input size is smaller than the shared memory, and pass through all data written to the shared memory to the standard output.

Usage

write-shm [OPTION...]

Options:

• -n, --name: Specifies the name of the shared memory (mandatory)
• -s, --semaphore: Enables protection of the shared memory with an existing named semaphore to prevent simultaneous access.
• -i, --invert: Inverts all input bits
• -r, --repeat: Repeats input until the shared memory is completely filled. This option has no effect if the input size is greater or equal the size of the shared memory.
• -p, --passthrough: Outputs everything that is written to the shared memory to standard output.

Examples

Example 1

echo "Hello, World!" | write-shm -n my_shared_memory

Writes "Hello, World!" to a shared memory named my_shared_memory.

Example 2

write-shm -n my_shm -s my_sem < data.bin

Write the binary file data.bin to a shared memory segment named my_shm and protect it with the semaphore my_sem.

Example 3

write-shm -n my_shm < /dev/zero

This command writes an infinite stream of null bytes from /dev/zero to the shared memory segment named my_shm. Therefore, every bit of my_shm is set to 0.

Example 4

write-shm -n my_shm -i < /dev/zero

This command writes an infinite stream of inverted null bytes from /dev/zero to the shared memory segment named my_shm. Therefore, every bit of my_shm is set to 1.

Example 5

write-shm -n my_shm -s my_sem < /dev/urandom > data.bin

This command writes a stream of pseudorandom bytes from /dev/urandom to the shared memory segment named my_shm while protecting it with the semaphore my_sem. Additionally, it saves the same data to a file named data.bin.

Example 6

write-shm -n my_shm -s my_sem -r < small_data.bin

This command writes the content of the file small_data.bin to the shared memory segment named my_shm. If the size of small_data.bin is smaller than the shared memory size, the input will be repeated to fill the shared memory segment. Additionally, it will be protected by the semaphore my_sem to prevent simultaneous access.

Install

Using the Arch User Repository (recommended for Arch based Linux distributions)

The application is available as write-shm in the Arch User Repository. See the Arch Wiki for information about how to install AUR packages.

Using the Modbus Collection Package: SHM Modbus

SHM Modbus is a collection of multiple tools to simulate a Modbus client.

Flatpak

The Flatpak package is available via Flathub as io.github.shmmodbus.shm-modbus.

write-shm is invoked by executing the following command:

flatpak run io.github.shmmodbus.shm-modbus write-shm

Snap

The snap package can be downloaded via the github release page.

write-shm is invoked by executing the following command:

shm-modbus.write-shm