The wcsncat_s
function in C appends a specified number of characters from a given wide string to the end of another wide string. The wcsncat_s
function also appends a null-terminating character to the end of the destination string after the concatenation is finished.
If the number of characters to append exceeds the destination string’s size, the wcsncat_s
function raises an error.
The process is illustrated below:
Note: A wide string is comprised of characters from the Unicode character set.
To use the wcsncat_s
function, you will need to include the <wchar.h>
library in the program, as shown below:
#include <wchar.h>
The prototype of the wcsncat_s
function is shown below:
errno_t *wcsncat_s(wchar_t *dest, rsize_t numElements, const wchar_t *src, rsize_t count);
The wcsncat_s
function takes the following objects as parameters:
dest
: null-terminated destination string to append tonumElements
: the size of the destination stringsrc
: null-terminated source string to copy fromcount
: the maximum number of characters to copy from src
to dest
The wcsncat_s
function appends the specified number of characters to the dest
string and returns if the operation is successful; otherwise, it returns a non-zero value and writes the null-terminating character to dest
.
The wcsncat_s
function will raise an error in the following situations:
src
or dest
are null
pointers.numElements
or count
is .count
is greater than the size of the destination string. We can avoid this by giving the count
parameter a value of _TRUNCATE, in which case wcsncat_s
will only append the number of characters that the destination string can safely hold.src
and dest
strings overlap.The code below shows how the wcsncat_s
function works in C:
#define __STDC_WANT_LIB_EXT1__ 1#include <stdio.h>#include <wchar.h>#include <string.h>int main() {// initializing stringswchar_t src[] = L"World";wchar_t dst[20] = L"Hello";// concatenating stringswcsncat_s(dst, 20, src, wcslen(src));return 0;}
First, two wide strings are initialized for the source and destination addresses. The ‘L’ identifier in lines 9 and 10 informs the compiler that the Unicode character set is being used.
The wcsncat_s
function proceeds to copy the entire source string to the destination address in line 13. The argument 20
specifies that the destination string can hold a maximum of characters. The wcslen
function finds the length of the source string so that the entire string is appended to dest
. After the src
string is appended, the wcsncpy_s
function adds a null-terminating character to dest
.
The GCC compiler does not support the function in the example above; hence you will get an implicit declaration of function…
error. Use the following variant to get the job done:
wchar_t* wcsncat(wchar_t* dest, const wchar_t* src, size_t count);
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