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STRCPY(3)                BSD Library Functions Manual                STRCPY(3)

NAME
     stpcpy, stpncpy, strcpy, strncpy -- copy strings

LIBRARY
     Standard C Library (libc, -lc)

SYNOPSIS
     #include <string.h>

     char *
     stpcpy(char *dst, const char *src);

     char *
     stpncpy(char *restrict dst, const char *restrict src, size_t n);

     char *
     strcpy(char *restrict dst, const char *restrict src);

     char *
     strncpy(char *restrict dst, const char *restrict src, size_t n);

DESCRIPTION
     The stpcpy() and strcpy() functions copy the string src to dst (including the terminating `\0' charac-ter). character).
     ter).

     The stpncpy() and strncpy() functions copy at most n characters from src into dst.  If src is less than
     n characters long, the remainder of dst is filled with `\0' characters.  Otherwise, dst is not termi-nated. terminated.
     nated.

     The source and destination strings should not overlap, as the behavior is undefined.

RETURN VALUES
     The strcpy() and strncpy() functions return dst.  The stpcpy() and stpncpy() functions return a pointer
     to the terminating `\0' character of dst.  If stpncpy() does not terminate dst with a NUL character, it
     instead returns a pointer to dst[n] (which does not necessarily refer to a valid memory location.)

EXAMPLES
     The following sets chararray to ``abc\0\0\0'':

           char chararray[6];

           (void)strncpy(chararray, "abc", sizeof(chararray));

     The following sets chararray to ``abcdef'':

           char chararray[6];

           (void)strncpy(chararray, "abcdefgh", sizeof(chararray));

     Note that it does not NUL terminate chararray, because the length of the source string is greater than
     or equal to the length argument.

     The following copies as many characters from input to buf as will fit and NUL terminates the result.
     Because strncpy() does not guarantee to NUL terminate the string itself, this must be done explicitly.

           char buf[1024];

           (void)strncpy(buf, input, sizeof(buf) - 1);
           buf[sizeof(buf) - 1] = '\0';

     This could be better achieved using strlcpy(3), as shown in the following example:

           (void)strlcpy(buf, input, sizeof(buf));

SECURITY CONSIDERATIONS
     The strcpy(), strncpy(), stpcpy(), and stpncpy() functions are easily misused in a manner which enables
     malicious users to arbitrarily change a running program's functionality through a buffer overflow
     attack.  (See the FSA and EXAMPLES.)

     It is recommended that strlcpy(3) be used instead as a way to avoid such problems.  strlcpy(3) is not
     defined in any standards, but it has been adopted by most major libc implementations.

SEE ALSO
     bcopy(3), memccpy(3), memcpy(3), memmove(3), strlcpy(3), wcscpy(3)

STANDARDS
     The strcpy() and strncpy() functions conform to ISO/IEC 9899:1990 (``ISO C90'').  The stpcpy() and
     stpncpy() functions conform to IEEE Std 1003.1-2008 (``POSIX.1'').

HISTORY
     The stpcpy() function first appeared in FreeBSD 4.4, and stpncpy() was added in FreeBSD 8.0.

BSD                            February 28, 2009                           BSD