strncat.c File Reference

#include <string.h>

Include dependency graph for strncat.c:

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Functions
char *	strncat (char *__restrict dst, const char *__restrict src, size_t maxlen)
	Appends at most maxlen characters from the character array pointed to by src, to the end of the null-terminated byte string pointed to by dest. More...

Function Documentation

strncat()

char* strncat	(	char *__restrict	dst,
		const char *__restrict	src,
		size_t	maxlen
	)

Appends at most maxlen characters from the character array pointed to by src, to the end of the null-terminated byte string pointed to by dest.

Appends at most count characters from the character array pointed to by src, stopping if the null character is found, to the end of the null-terminated byte string pointed to by dest. The character src[0] replaces the null terminator at the end of dest. The terminating null character is always appended in the end (so the maximum number of bytes the function may write is maxlen+1).

The behavior is undefined if the destination array is not large enough for the contents of both src and dest and the terminating null character. The behavior is undefined if the strings overlap. The behavior is undefined if either dest or src is not a pointer to a null-terminated byte string.

Parameters

dst	pointer to the null-terminated byte string to append to
src	pointer to the null-terminated byte string to copy from
maxlen	maximum number of characters to copy

Returns

a copy of dest

Definition at line 26 of file strncat.c.

{
    const size_t dstlen = strlen(dst);
    const size_t srclen = strnlen(src, maxlen);
    //  The strcat() and strncat() functions append a copy of the null-
    //  terminated string src to the end of the null-terminated string dst,
    //  then add a terminating '\0'.  The string dst must have sufficient
    //  space to hold the result.
    //
    //  The strncat() function appends not more than maxlen characters
    //  from src, and then adds a terminating '\0'.
    const size_t cpylen = srclen < maxlen ? srclen : maxlen;
    memcpy(dst + dstlen, src, cpylen);
    dst[dstlen + cpylen] = '\0';
    //  The strcat() and strncat() functions return dst.
    return dst;
}

References memcpy(), strlen(), and strnlen().