strncat(3P, 3p)	concatenate a string with part of another
strncat(3)	append non-null bytes from a source array to a string, and null-terminate the result
stpecpy, stpecpyx, string_copying, ustpcpy, ustr2stp, zustr2stp, zustr2ustp, stpcpy, stpncpy, strcat, strcpy, strlcat, strlcpy, strncat, strncpy, strtcpy(3, 7)	copying strings and character sequences
string, stpcpy, index, rindex, strcasecmp, strcat, strchr, strcmp, strcoll, strcpy, strcspn, strdup, strfry, strlen, strncasecmp, strncat, strncmp, strncpy, strpbrk, strrchr, strsep, strspn, strstr, strtok, strxfrm(3)	string operations

NAME

strncat - append non-null bytes from a source array to a string, and null-terminate the result

LIBRARY

Standard C library (libc, -lc)

SYNOPSIS

#include <string.h>

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.

An implementation of this function might be:

char *
strncat(char *restrict dst, const char *restrict src, size_t ssize)
{


    #define strnul(s)  (s + strlen(s))


    stpcpy(mempcpy(strnul(dst), src, strnlen(src, ssize)), "");


    return 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).

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).

BUGS

This function can be very inefficient. Read about Shlemiel the painter.

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);
}