NAME
strncat - nonstring catenate
LIBRARY
Standard C library (libc, -lc)
SYNOPSIS
#include <string.h> // see memory.h(3head)
char *strncat(size_t ssize; char *restrict dst, const char src[restrict ssize], size_t ssize);
DESCRIPTION
This function appends at most ssize non-null bytes from the array pointed to by src, followed by a null character, to the end of the string pointed to by dst. dst must point to a string contained in a buffer that is large enough, that is, the buffer size must be at least strlen(dst) + strnlen(src, ssize) + 1.
It is equivalent to
stpcpy(mempcpy(strnul(dst), src, strnlen(src, ssize)), ""), dst
RETURN VALUE
strncat() returns dst.
ATTRIBUTES
For an explanation of the terms used in this section, see attributes(7).
| Interface | Attribute | Value |
| strncat() | Thread safety | MT-Safe |
STANDARDS
C11, POSIX.1-2008.
HISTORY
POSIX.1-2001, C89, SVr4, 4.3BSD.
CAVEATS
The name of this function is confusing:
- •
-
It has no relation to strncpy(3).
- •
-
It doesn't truncate the input nonstring.
If the destination buffer does not already contain a string, or is not large enough, the behavior is undefined. See _FORTIFY_SOURCE in feature_test_macros(7).
EXAMPLES
#include <stdcountof.h>
#include <stdio.h>
#include <string.h>
#include <utmp.h>
void print_ut_user(struct utmp *ut);
void
print_ut_user(struct utmp *ut)
{
char buf[countof(ut->ut_user) + 1];
strcpy(buf, "");
strncat(buf, ut->ut_user, countof(ut->ut_user));
puts(buf);
}