In Linux command-line environments, the cat command is a versatile tool primarily used to display the contents of files. However, when used with a hyphen - as an argument ‘cat -‘ its behavior changes significantly.
cat –
The hyphen - serves as a signal to cat that it should read from standard input (stdin) instead of from a specified file. This allows for dynamic input directly from the terminal.
When we execute cat -, the command-line interface awaits further instructions or input. Since cat typically supports various options and expects file names as arguments, the presence of - triggers the system to anticipate additional directives.
cat - is often used in conjunction with other commands or in pipelines, where it acts as a conduit for passing data between commands. Furthermore, it’s particularly useful when we need to provide input interactively or when dealing with dynamic data streams.
Upon executing the following command:
e@e:~/Desktop$ cat –
We may observe that the terminal seemingly “waits” indefinitely as shown below. This is because the system anticipates further input or instructions from the user.
Without providing additional input or options, cat - appears to be in a state of limbo, awaiting guidance from the user even if we echo random commands or words it will still repeat them and wait for instructions as shown below.
Interacting With The File
Although cat - itself doesn’t directly open a file, we can access the content it represents through alternative methods.
One way is to use the relative path, such as:
e@e:~/Desktop$ cat ./-
Or the absolute path, like:
e@e:~/Desktop$ cat /home/e/Desktop/-
As we can see when we specified the relative or absolute path we was able to extract the file content. Additionally, by understanding the nuances of cat - and its interaction with standard input, we gain a deeper understanding of command-line utilities and their flexibility in handling data streams.
Giving Information
As we solved the previous Bandit 1 challenge, we obtained the password for this machine. We also have the machine hostname required for SSH access:
- Machine Hostname: bandit1@bandit.labs.overtherwire.org
- Password: NH2SXQwcBdpmTezi3bvBHMM9H66vVXjL
- Flag Location: The password for the next level is stored in a file called
-located in the home directory.
Finding The Flag
To access the machine, we SSH using the following command:
e@e:~/Desktop$ ssh -p 2220 bandit1@bandit.labs.overthewire.org
We provide the password obtained from the previous machine:
e@e:~/Desktop$ NH2SXQwcBdpmTezi3bvBHMM9H66vVXjL
Upon successful access, we list the files in the home directory:
bandit1@bandit:~$ ls -l
We find a file named - storing the required password. Let’s attempt to view its content using the following command:
bandit1@bandit:~$ cat –
However, the terminal waits indefinitely for our input, as discussed earlier. Lets try to input something and see what we get
Still nothing! So lets try to use the relative file path using the following command:
bandit1@bandit:~$ cat ./-
We can also use the absolute file path and get the same result using the following command:
bandit1@bandit:~$ cat /home/bandit1/-
In conclusion, despite encountering a file with a dashed filename, we successfully extracted the required information by utilizing alternative methods. This highlights the flexibility and adaptability of command-line utilities in handling various file naming conventions.
If you’re ready to move on to the next Bandit level, you can click here.