#include <string.h>

       char *strcat(char *dest, const char *src);

       char *strncat(char *dest, const char *src, size_t n);

       The  strcat() function appends the src string to the dest string, over-
       writing the terminating null byte ('\0') at the end of dest,  and  then
       adds  a  terminating  null  byte.  The strings may not overlap, and the
       dest string must have enough space for the  result.   If  dest  is  not
       large  enough, program behavior is unpredictable; buffer overruns are a
       favorite avenue for attacking secure programs.

       The strncat() function is similar, except that

       *  it will use at most n bytes from src; and

       *  src does not need to be null-terminated if it  contains  n  or  more

       As  with  strcat(),  the resulting string in dest is always null-termi-

       If src contains n or more bytes, strncat() writes n+1 bytes to dest  (n
       from  src plus the terminating null byte).  Therefore, the size of dest
       must be at least strlen(dest)+n+1.

       A simple implementation of strncat() might be:

           char *
           strncat(char *dest, const char *src, size_t n)
               size_t dest_len = strlen(dest);
               size_t i;

               for (i = 0 ; i < n && src[i] != '\0' ; i++)
                   dest[dest_len + i] = src[i];
               dest[dest_len + i] = '\0';

               return dest;

       The strcat() and strncat() functions return a pointer to the  resulting
       string dest.

       For   an   explanation   of   the  terms  used  in  this  section,  see

       |Interface           | Attribute     | Value   |
       dest, copying at most size-strlen(dest)-1 from src, and adds  a  termi-
       nating  null byte to the result, unless size is less than strlen(dest).
       This function fixes the buffer overrun problem  of  strcat(),  but  the
       caller  must  still  handle the possibility of data loss if size is too
       small.  The function returns the length of the string  strlcat()  tried
       to  create;  if the return value is greater than or equal to size, data
       loss occurred.  If data loss matters, the caller must either check  the
       arguments  before  the  call, or test the function return value.  strl-
       cat() is not present in glibc and is not standardized by POSIX, but  is
       available on Linux via the libbsd library.

       bcopy(3),  memccpy(3),  memcpy(3),  strcpy(3),  string(3),  strncpy(3),
       wcscat(3), wcsncat(3)

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GNU                               2015-08-08                         STRCAT(3)
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