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# Bash String Is Not Empty
The `-n` operator is a unary string evaluation operator in Bash that tests whether a given string has a non-zero length. When executed within a test command construct, it returns an exit status of `0` (true) if the string contains one or more characters, and an exit status of `1` (false) if the string is empty (null) or an unassigned variable.
**Syntax**
```bash theme={"dark"}
[ -n "$VARIABLE" ]
[[ -n "$VARIABLE" ]]
test -n "$VARIABLE"
```
**Evaluation Mechanics**
* **Operand:** Accepts a single string argument.
* **Return Value:** Yields `0` (success/true) for `length > 0`. Yields `1` (failure/false) for `length == 0`.
* **Inverse:** The `-n` operator is the exact logical inverse of the `-z` operator, which tests for a zero-length string.
**Parsing and Quoting Nuances**
When using the POSIX-compliant single bracket `[ ]` or the `test` builtin, the string operand must be enclosed in double quotes (`"$VARIABLE"`). If the variable is unquoted and evaluates to null, the shell performs word splitting before the test command executes. This expands the expression to `[ -n ]`.
In this unquoted scenario, Bash's parsing rules interpret the isolated `-n` as a literal non-empty string argument rather than a unary operator, erroneously returning an exit status of `0`.
```bash theme={"dark"}
# Incorrect: Evaluates to true (0) even if VAR is empty due to word splitting
[ -n $VAR ]
# Correct: Safely evaluates to false (1) if VAR is empty
[ -n "$VAR" ]
```
When using the Bash-specific double bracket `[[ ]]` (extended test command), word splitting and pathname expansion are suppressed. Consequently, `[[ -n $VAR ]]` will correctly evaluate to false if the variable is empty. However, double-quoting the variable remains the standard technical convention to ensure predictable behavior across different shell environments and test constructs.
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