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STRCAT(3)                  Linux Programmer's Manual                 STRCAT(3)

NAME
       strcat, strncat - concatenate two strings
SYNOPSIS
       #include <string.h>
       char *strcat(char *dest, const char *src);
       char *strncat(char *dest, const char *src, size_t n);
DESCRIPTION
       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
          bytes.
       As  with  strcat(),  the resulting string in dest is always null-termi-
       nated.
       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;
           }
RETURN VALUE
       The strcat() and strncat() functions return a pointer to the  resulting
       string dest.
CONFORMING TO
       SVr4, 4.3BSD, C89, C99.
NOTES
       Some  systems  (the  BSDs,  Solaris,  and others) provide the following
       function:
           size_t strlcat(char *dest, const char *src, size_t size);
       This function appends the null-terminated  string  src  to  the  string
       dest,  copying  at  most  size-strlen(dest)-1 from src, and adds a null
       terminator 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 cre-
       ate; if the return value is greater than or equal to  size,  data  loss
       occurred.  If data loss matters, the caller must either check the argu-
       ments before the call, or test the function return value.  strlcat() is
       not present in glibc and is not standardized by POSIX, but is available
       on Linux via the libbsd library.
SEE ALSO
       bcopy(3),  memccpy(3),  memcpy(3),  strcpy(3),  string(3),  strncpy(3),
       wcscat(3), wcsncat(3)
COLOPHON
       This  page  is  part of release 3.53 of the Linux man-pages project.  A
       description of the project, and information about reporting  bugs,  can
       be found at http://www.kernel.org/doc/man-pages/.

GNU                               2012-07-19                         STRCAT(3)