# cString(using:) Returns a representation of the string as a C string using a given encoding. ``` func cString(using encoding: UInt) -> UnsafePointer? ``` ## Parameters `encoding` The encoding for the returned C string. For possible values, see [`NSStringEncoding`](/documentation/Foundation/NSStringEncoding). ## Return Value A C string representation of the receiver using the encoding specified by `encoding`. Returns `NULL` if the receiver cannot be losslessly converted to `encoding`. ## Discussion The returned C string is guaranteed to be valid only until either the receiver is freed, or until the current memory is emptied, whichever occurs first. You should copy the C string or use [`getCString(_:maxLength:encoding:)`](/documentation/Foundation/NSString/getCString(_:maxLength:encoding:)) if it needs to store the C string beyond this time. You can use [`canBeConverted(to:)`](/documentation/Foundation/NSString/canBeConverted(to:)) to check whether a string can be losslessly converted to `encoding`. If it can’t, you can use [`data(using:allowLossyConversion:)`](/documentation/Foundation/NSString/data(using:allowLossyConversion:)) to get a C-string representation using `encoding`, allowing some loss of information (note that the data returned by [`data(using:allowLossyConversion:)`](/documentation/Foundation/NSString/data(using:allowLossyConversion:)) is not a strict C-string since it does not have a `NULL` terminator). ### Special Considerations UTF-16 and UTF-32 are not considered to be C string encodings, and should not be used with this method—the results of passing [`NSUTF16StringEncoding`](/documentation/Foundation/NSUTF16StringEncoding), [`NSUTF32StringEncoding`](/documentation/Foundation/NSUTF32StringEncoding), or any of their variants are undefined. ## See Also [`canBeConverted(to:)`](/documentation/Foundation/NSString/canBeConverted(to:)) Returns a Boolean value that indicates whether the receiver can be converted to a given encoding without loss of information. [`getCString(_:)`](/documentation/Foundation/NSString/getCString(_:)) Invokes [`getCString(_:maxLength:range:remaining:)`](/documentation/Foundation/NSString/getCString(_:maxLength:range:remaining:)) with `NSMaximumStringLength` as the maximum length, the receiver’s entire extent as the range, and `NULL` for the remaining range. [`cStringLength()`](/documentation/Foundation/NSString/cStringLength()) Returns the length in char-sized units of the receiver’s C-string representation in the default C-string encoding. [`defaultCStringEncoding`](/documentation/Foundation/NSString/defaultCStringEncoding) Returns the C-string encoding assumed for any method accepting a C string as an argument. --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)