> ## Documentation Index
> Fetch the complete documentation index at: https://docs.syntblaze.com/llms.txt
> Use this file to discover all available pages before exploring further.
# Bash Case Modification
The `^^` operator is a parameter expansion modifier in Bash (version 4.0 and later) that converts lowercase characters in a variable's value to uppercase during expansion. It evaluates the string against an optional glob pattern and applies the case transformation to every matching character across the entire string.
```bash theme={"dark"}
${parameter^^pattern}
${parameter^^}
```
## Mechanics and Behavior
* **`parameter`**: The identifier of the variable being expanded.
* **`pattern`**: A standard Bash pathname expansion (globbing) pattern. The pattern is evaluated against each individual character in the expanded string, not the string as a whole.
* **Default Evaluation**: If `pattern` is omitted, Bash implicitly uses the `?` glob pattern, which matches and converts every character in the string.
* **Non-destructive Execution**: The operator performs an in-memory transformation during the evaluation step. It does not mutate the underlying value stored in `parameter`.
* **Array Propagation**: When applied to an indexed or associative array using the `@` or `*` subscripts (`${array[@]^^}`), the operator iterates through the array and applies the uppercase transformation to the value of every element individually.
## Syntax Examples
**Global Conversion (Omitted Pattern)**
Omitting the pattern converts all characters.
```bash theme={"dark"}
str="alpha beta"
echo "${str^^}"
# Output: ALPHA BETA
```
**Targeted Conversion (Explicit Pattern)**
Providing a pattern restricts the transformation to matching characters.
```bash theme={"dark"}
str="alpha beta"
echo "${str^^[aeiou]}"
# Output: AlphA bEtA
```
**Array Expansion**
Applying the operator to the `@` subscript transforms all elements.
```bash theme={"dark"}
arr=("foo" "bar" "baz")
echo "${arr[@]^^}"
# Output: FOO BAR BAZ
```
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