STRCPY(3) | Library Functions Manual | STRCPY(3) |
stpcpy
, stpncpy
,
strcpy
, strncpy
—
#include <string.h>
char *
stpcpy
(char
* restrict dst, const
char * restrict src);
char *
stpncpy
(char
* restrict dst, const
char * restrict src,
size_t len);
char *
strcpy
(char
* restrict dst, const
char * restrict src);
char *
strncpy
(char
* restrict dst, const
char * restrict src,
size_t len);
stpcpy
() and strcpy
()
functions copy the string src to
dst (including the terminating
‘\0
’ character).
The stpncpy
() and
strncpy
() functions copy at most
len characters from src into
dst. If src is less than
len characters long, the remainder of
dst is filled with
‘\0
’ characters. Otherwise,
dst is not terminated.
The strings src and dst may not overlap.
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[len]
(which does not necessarily refer to a valid memory location.)
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 parameter.
strncpy
() only
NUL
-terminates the
destination string when the length of the source string is less than the
length parameter.
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 and more simply achieved using strlcpy(3), as shown in the following example:
(void)strlcpy(buf, input, sizeof(buf));
Note that because strlcpy(3) is not defined in any standards, it should only be used when portability is not a concern.
strcpy
() and strncpy
()
functions conform to ISO/IEC 9899:1999
(“ISO C99”). The stpcpy
()
and stpncpy
() functions conform to
IEEE Std 1003.1-2008 (“POSIX.1”).
stpcpy
() and stpncpy
()
functions first appeared in NetBSD 6.0.
strcpy
() and stpcpy
()
functions are easily misused in a manner which enables malicious users to
arbitrarily change a running program's functionality through a buffer overflow
attack.
April 1, 2015 | NetBSD 9.2 |