Using the unbraced form $var for variable references can lead to several problems in shell scripts.
First, it creates inconsistency in your code. When some variables use $var and others use ${var}, the script becomes
harder to read and maintain. Consistent formatting helps developers quickly understand the code structure.
Second, the unbraced form can cause ambiguity issues. Consider a scenario where you want to append text directly after a variable name, like
$varname_suffix. The shell interpreter cannot determine where the variable name ends and the literal text begins. This often leads to
unexpected behavior or empty output.
Third, using braces makes your intentions explicit. The ${var} form clearly delimits the variable name, making the code more readable
and less prone to parsing errors. This is especially important in complex expressions or when variables are embedded within strings.
Finally, adopting the braced form as a standard practice prepares your code for more advanced parameter expansion features that shell provides,
such as ${var:-default} or ${var#prefix}. Starting with consistent bracing makes it easier to enhance your scripts
later.
What is the potential impact?
Using unbraced variable references can lead to:
- Unexpected behavior when variable names are followed by characters that could be part of the variable name
- Reduced code readability and maintainability
- Inconsistent coding style across the codebase
- Potential bugs when refactoring or extending variable usage
