Advanced Bash Scripting
Conventions
Variables
Proper variable management in Bash scripts improves readability, prevents accidental overwrites, and makes your code easier to maintain. In this guide, you’ll learn best practices for naming variables, defining constants, and exporting values for child processes.
Table of Contents
1. Naming Conventions
Follow these guidelines to create clear, self-documenting variable names:
| Convention | Description | Example |
|---|---|---|
| Lowercase | All variable names in lowercase to avoid conflicts | username="alice" |
| Snake case | Use underscores for multi-word names | first_name_last_name="Alice" |
| Descriptive names | Reflect the variable’s purpose | config_file="/etc/app.conf" |
| Single-letter (optional) | Only for simple counters or arithmetic operations | x=10 |
Example:
first_name_last_name="Alice"
source_file="/etc/config.yaml"
count=42
x=10
Note
Avoid uppercase names for regular variables—uppercase is conventionally reserved for constants (see Defining Constants).
2. Defining Constants
When you have values that should never change, define them in uppercase snake_case and mark them as read-only:
readonly FILE_NAME="file.txt"
readonly MAX_RETRIES=5
readonly PI=3.14159
Using readonly serves two purposes:
- Clarity: Signals to readers that these values are fixed.
- Safety: Prevents accidental reassignment later in the script.
Warning
Attempting to modify a readonly variable will produce an error:
PI=3.14 # bash: PI: readonly variable
3. Exporting Variables
Export variables when you need them in child processes, subshells, or external scripts.
Export an existing variable
source_file="/etc/config.yaml"
export source_file
Define and export in one step
export HOME_DIR="/home/user"
Exported variables become part of the environment for all subsequent commands and processes started from the current shell.
4. References
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