---
title: "withCString(_:)"
framework: swift
role: symbol
role_heading: Instance Method
path: "swift/stringprotocol/withcstring(_:)"
---

# withCString(_:)

Calls the given closure with a pointer to the contents of the string, represented as a null-terminated sequence of UTF-8 code units.

## Declaration

```swift
func withCString<Result>(_ body: (UnsafePointer<CChar>) throws -> Result) rethrows -> Result
```

## Parameters

- `body`: A closure with a pointer parameter that points to a null-terminated sequence of UTF-8 code units. If body has a return value, that value is also used as the return value for the withCString(_:) method. The pointer argument is valid only for the duration of the method’s execution.

## Return Value

Return Value The return value, if any, of the body closure parameter.

## Discussion

Discussion The pointer passed as an argument to body is valid only during the execution of withCString(_:). Do not store or return the pointer for later use.