Bash variable interpolation: a guide for shell programmers

If you're a shell programmer working with Bash, you'll know that variable interpolation is a crucial part of working with shell scripts. In short, variable interpolation is the process of inserting the value of a variable into a string or command, allowing you to dynamically build commands and output strings.

  1. Syntax
  2. Escaping
  3. Brace expansion
  4. Conclusion


The syntax for variable interpolation is fairly simple. To interpolate a variable, simply prefix its name with a dollar sign ($), like so:

echo "Hello, $USER"

This will output "Hello, " followed by the value of the $USER variable. Note that you don't need to use any special syntax to interpolate variables in strings - simply including the variable name in the string is enough.


Sometimes, you'll want to include a literal dollar sign in your output string, without actually interpolating a variable. In these cases, you'll need to escape the dollar sign with a backslash (), like so:

echo "You owe me $10"

This will output "You owe me $10".

Brace expansion

Bash also supports a feature called brace expansion, which allows you to generate multiple values from a single expression. For example:

echo {1..5}

This will output "1 2 3 4 5". You can also use brace expansion to generate filenames, like so:

touch file{1..5}.txt

This will create five files: file1.txt, file2.txt, file3.txt, file4.txt, and file5.txt.


Variable interpolation is a powerful feature of Bash that allows you to build dynamic commands and output strings. By mastering the syntax and techniques involved, you can become a more efficient and effective shell programmer.

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