---
name: uc
status: documented
runtime: pp
source: src/runtime/pp/strings/case.rs
---
```{index} single: uc; Perl built-in (pp runtime)
```

# uc

## Synopsis

```perl
$upper = uc($string);
$upper = uc('hello');   # "HELLO"
```

## Description

Converts a string to uppercase.

Returns an uppercased copy of STRING. For ASCII input, an in-place
byte mutation fast path avoids allocation when a TARG pad slot is
available. For Unicode input, Rust's `to_uppercase()` is used, which
handles case mappings that change byte length (e.g. the German
sharp-s `\u{00DF}` becomes `"SS"`).

## See also

lc, ucfirst, lcfirst