Bash Define Multiline String Variable

Let’s assume you have encountered a scenario where you need to define a multiline block of string in your Bash scripting operations. If you try the default way of defining a variable in Bash, you are bound to encounter an error or an incomplete part of the variable.

This quick guide will show you methods of defining multiline string variables using escape characters and Heredoc.

Bash Escape Characters

Bash, like most programming languages, provides the ability to use escape characters. Escape characters allow us to invoke a new interpretation of character sequences. Although Bash has various escape characters, we only need to concern ourselves with \n (new line character).

For example, if we have a multiline string in a script, we can use the \n character to create a new line where necessary.

An example of such a use case is:

Executing the above script prints the strings in a new line where the \n character exists.

HereDoc

The above method works fine for simple line text. However, if we need to print a text with other special characters, backlashes, and quotes, it becomes unnecessarily complex. To solve such an issue, we can use HereDoc.

What is a Heredoc?

A heredoc is a special-purpose code block that tells the shell to read input from the current source until it encounters a line containing a delimiter.

The syntax for Heredoc in Bash is:

Delimiters in a Heredoc can be any string. However, the most common strings are EOF, EOM, or END.

Once the shell encounters the delimiter, it replaces all the variables, commands, and special characters and then passes the information inside the Heredoc block to the main command.

You can include special characters, regular strings, variables, and other shell commands in the Heredoc block.

Ensure to terminate the Heredoc block with the delimiter. Do not add any whitespace before the delimiter.

Multiline String Using Heredoc

Suppose you have the following string:

Inside a bash script, we can create a varible and pass the string above to cat as shown below:

Once you run the above script, you will see an output a:

As you can see, we can print the entire string, including all special characters.

Conclusion

For this guide, we discussed how to define and use a multiline string in a bash script. However, there is more to Heredoc than discussed here. Consider the following resource to learn more.