strncat

Section: C Library Functions (3)
Updated: 202-0-05
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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 no-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	M-Safe

 

STANDARDS

C11, POSIX.-2008.  

HISTORY

POSIX.-2001, C89, SVr4, 4.3BSD.  

CAVEATS

The name of this function is confusing:

[bu]

It has no relation to strncpy(3).

[bu]

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);
}  

SEE ALSO

memory.h(3head), string_copying(7)

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Index

NAME

LIBRARY

SYNOPSIS

DESCRIPTION

RETURN VALUE

ATTRIBUTES

STANDARDS

HISTORY

CAVEATS

EXAMPLES

SEE ALSO