Base64 Encode and Decode From Command Line

Encoding is the process used to convert data in a format required for effective transmission or storage. In contrast, decoding is opposite to the encoding method which converts the encoded data back to its original format. Base64 is the encoding process where the binary data is converted into ASCII. Base64 encoding is mostly required to avoid the transmission problems that occur when binary data is transmitted to text-based systems which cannot handle the binary data properly. As a result, the information is lost or corrupted during transmission.

Some of the uses of encoding are:

• Data compression
• Data hiding
• Transmission of data in another format

For encoding data, Base64 uses only alphabet, number and = symbol. For instance, c2FtcGxlCg== is a valid encoded data while b?HV3.Zh2J== is not a valid encoded data.

In this article, we will explain how to use the base64 command to encode and decode the data in a string or a file.

We have performed the commands on Ubuntu 20.04 Focal Fossa system. However, you can also run the same commands on other Linux distributions. For running the commands, we have used the command line Terminal application, which can be accessed using the Ctrl+Alt+T keyboard shortcut.

Base64 Syntax

Here is the syntax for encoding using Base64:

Options

Some of the command-line options that can be used with base64 command are:

Use this option to decode a file or a string.

Use this option to display help regarding the usage of base64.

Use this option while decoding to ignore non-alphabet characters

Use this option to display version information

Encoding String

You can easily encode a string using the base64 command. For instance, to encode a sample text “Welcome to Linux” to base64, the command would be:

This command will encode the text in the string using base64 and print the encoded text to standard output as shown in the following screenshot

You can also save the encoded output to a file rather than printing to standard output using the redirection operator (>). The following command will encode the text and save the output to a file named “encodedfile.txt:

To view the encoded file, you can use the cat command:

Decoding String

You can also decode the base64 encoded text using the –decode or -d option. For instance to decode base64 encoded text “V2VsY29tZSB0byBMaW51eAo=”, the command would be:

This command will decode the base64 encoded text and print the original text on the standard output as shown in the following screenshot.

You can also save the decoded output to a file rather than printing to standard output using the redirection operator (>). The following command will decode the encoded text and save the original text to a file named “decodedfile.txt:

Encoding Text File

The base64 command can also be used to encode a text file. For instance, to encode a text file named “testfile.txt”, the command would be:

This command will encode the specified text file and print its encoded form on the standard output as shown in the following screenshot.

You can also save the encoded output to a file rather than printing to standard output using the redirection operator (>). The following command will convert the text in the file using base64 and save the output to another file named “encodedfile.txt:

To view the encoded file, you can use the cat command:

Decoding Text File

To decode an encoded text file, use the –decode or -d option. For instance to decode base64 encoded text file “encodedfile.txt”, the command would be:

This command will decode the base64 encoded text file and print the original text on the standard output as shown in the following screenshot.

You can also save the decoded output to a file rather than printing to standard output using the redirection operator (>). The following command will decode the encoded text and save the original text to a file named “decodedfile.txt which can be later viewed using the cat command.

Encoding User Input

Using the base64 encoding, we can encode any user-provided data. For this purpose, we will need to create a script that will take user input, encode it using base64 encoding, and print the encoded data on standard output.

Create a script “test.sh” with the following code:

Run the script as follows:

After running the script, you will be asked to input the data that you want to encode. Type some data and press Enter, and you will receive the encoded output on the screen.

Validating User key

Now let’s see an example of base64 decoding. We will use the base64 decoding to check user validity. To do so, we will create a script that will ask the user for a key. Then it will match the input key with the predefined key, which will be first decoded by base64 decoding. If the key entered by the user matches with the predefined key, it will print “You have entered a valid key” message, otherwise, you will see “The key you have entered is not valid “printed on the screen.

Create a script “test1.sh” with the following code:

Run the script as follows:

After running the script, you will be asked for the key. Type the key and press Enter. If the entered key matches with the predefined decoded key, you will receive the ” You have entered a valid key” message, otherwise “The key you have entered is not valid ” message will be printed on the screen.

This is how you can use the base64 to encode and decode a string or a file from the command line. The results can be either printed on the standard output or save in a file. However, remember that encoding is not similar to encryption, and one can easily reveal the encoded data, so it is not recommended to use encoding for the transmission of sensitive data.