WCSLCPY(3)

NAME
wcslcpy, wcslcat - size-bounded wide string copying and concatenation

SYNOPSIS
#include <wchar.h>
size_t
wcslcpy(wchar_t * restrict dst, const wchar_t * restrict src, size_t size);
size_t
wcslcat(wchar_t * restrict dst, const wchar_t * restrict src, size_t size);

DESCRIPTION
The wcslcpy() and wcslcat() functions copy and concatenate wide strings respectively. They are designed to be safer, more consistent, and less error prone replacements for wcsncpy(3) and wcsncat(3). Unlike those functions, wcslcpy() and wcslcat() take the full size of the buffer (not just the length) and guarantee to terminate the result with a null wide character (as long as size is larger than 0 or, in the case of wcslcat(), as long as there is at least one wide character free in dst). Note that a wide character for the null wide character should be included in size. Also note that wcslcpy() and wcslcat() only operate on wide strings that are terminated with a null wide character (L'\0'). This means that for wcslcpy() src must be terminated with a null wide character and for wcslcat() both src and dst must be terminated with a null wide character.

The wcslcpy() function copies up to size - 1 wide characters from the wide string src to dst, terminating the result with a null wide character.

The wcslcat() function appends the wide string src to the end of dst. It will append at most size - wcslen(dst) - 1 wide characters, terminating the result with a null wide character.

If the src and dst strings overlap, the behavior is undefined.

RETURN VALUES
The wcslcpy() and wcslcat() functions return the total length of the wide string they tried to create. For wcslcpy() that means the length of src. For wcslcat() that means the initial length of dst plus the length of src. While this may seem somewhat confusing, it was done to make truncation detection simple.

Note, however, that if wcslcat() traverses size wide characters without finding a null wide character, the length of the string is considered to be size and the destination wide string will not be terminated with a null wide character (since there was no space for it). This keeps wcslcat() from running off the end of a wide string. In practice this should not happen (as it means that either size is incorrect or that dst is not terminated with a null wide character). The check exists to prevent potential security problems in incorrect code.

SEE ALSO
strlcpy(3), swprintf(3), wcsncat(3), wcsncpy(3)

STANDARDS
The wcslcpy() and wcslcat() functions conform to p1003.1-2024.

HISTORY
The wcslcpy() and wcslcat() functions first appeared in OpenBSD 3.8.

AUTHORS
The wcslcpy() and wcslcat() functions are based on code by Todd C. Miller <millert@openbsd.org>.