Linux cu Command with Practical Examples

Introduction

In this lab, we will explore the cu command, a powerful tool in Linux for establishing remote connections and transferring files between systems. We will learn how to install the cu command, establish a connection using it, and transfer files between the local and remote systems. The lab covers the introduction to the cu command, establishing a connection, and transferring files with practical examples.

The cu command may require additional installation on some systems, as it is not always included by default. Additionally, while the cu command is still widely used, there are newer and more feature-rich alternatives available, such as screen or tmux, which may be more suitable for some use cases.

Linux Commands Cheat Sheet

Introduction to the cu Command

In this step, we will explore the cu command, which stands for "Call Up" or "Connect to". The cu command is a powerful tool in Linux for establishing remote connections and transferring files between systems. It can be used to connect to other systems, such as mainframes, minicomputers, or other Linux/Unix systems, over a serial line or modem.

To begin, let's first check if the cu command is installed on our system:

sudo apt-get update
sudo apt-get install -y cu

Example output:

Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
The following NEW packages will be installed:
  cu
0 upgraded, 1 newly installed, 0 to remove and 0 not upgraded.
Need to get 35.6 kB of archives.
After this operation, 112 kB of additional disk space will be used.
Get:1 http://archive.ubuntu.com/ubuntu jammy/main amd64 cu amd64 1.07-1 [35.6 kB]
Fetching and Extracting packages... Done
Setting up cu (1.07-1) ...

The cu command is now installed on our system, and we can start using it to connect to remote systems.

Establishing a Connection Using the cu Command

In this step, we will learn how to establish a connection using the cu command. The cu command can be used to connect to remote systems over a serial line or modem.

To establish a connection, we can use the following command:

sudo cu -l /dev/ttyUSB0 -s 9600

Here, the -l option specifies the serial device to use, and the -s option specifies the baud rate. You may need to adjust these options based on your specific setup.

Once the connection is established, you should see a prompt indicating that you are connected to the remote system. You can then interact with the remote system as if you were directly logged in.

To exit the cu session, type ~. (tilde followed by a period) and press Enter.

Example output:

Connected.
login:

Now, let's try to establish a connection using the cu command.

Transferring Files with the cu Command

In this step, we will learn how to transfer files using the cu command. The cu command can be used to send and receive files between the local and remote systems.

To transfer a file from the local system to the remote system, follow these steps:

Establish a connection to the remote system using the cu command:

sudo cu -l /dev/ttyUSB0 -s 9600

Once the connection is established, type ~> followed by the filename to send the file:

~>example.txt

This will initiate the file transfer process. The remote system will prompt you to start the file transfer.

To transfer the file, simply press Enter on the local system. The file will be transferred to the remote system.

Example output:

Connected.
~>example.txt
[remote system prompts]
[file transfer starts]

To receive a file from the remote system, follow these steps:

Establish a connection to the remote system using the cu command.
On the remote system, type ~< followed by the filename to initiate the file transfer.
On the local system, the file transfer will start automatically. The file will be saved in the current directory.

Example output:

Connected.
~<example.txt
[file transfer starts]
[file saved on local system]

Now, let's try to transfer a file using the cu command.

Summary

In this lab, we first explored the cu command, which is a powerful tool in Linux for establishing remote connections and transferring files between systems. We learned how to check if the cu command is installed on our system and how to install it if necessary.

Next, we focused on establishing a connection using the cu command. We covered the syntax for the cu command, including the -l option to specify the serial device and the -s option to specify the baud rate. We also learned how to exit the cu session by typing ~..

Linux Commands Cheat Sheet