string.h — String manipulation functions

The string.h header file declares the string manipulation functions and their built-in versions:

No feature test macro required.

_UNIX03_SOURCE

[1]  Built-in function.

_XOPEN_SOURCE

_XOPEN_SOURCE_EXTENDED 1

The string.h header file also defines the macro NULL and the type size_t. For more information see stddef.h — typedef statements.