STRCPY(3) | Library Functions Manual | STRCPY(3) |
stpcpy, stpncpy, strcpy
,
strncpy
— copy
strings
Standard C Library (libc, -lc)
#include
<string.h>
char *
stpcpy
(char
* dst, const char *
src);
char *
stpncpy
(char
* dst, const char *
src, size_t
len);
char *
strcpy
(char
* dst, const char *
src);
char *
strncpy
(char
* dst, const char *
src, size_t
len);
YOU SHOULD ALMOST CERTAINLY USE
strlcpy
()
INSTEAD.
See "Examples" below.
The
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 source and destination strings should not overlap, as the behavior is undefined.
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.)
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));
Note that because strlcpy(3) is not defined in any standards, it should only be used when portability is not a concern.
bcopy(3), memccpy(3), memcpy(3), memmove(3), strlcpy(3), wcscpy(3)
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”).
The stpcpy
() function first appeared in
FreeBSD 4.4, and stpncpy
()
was added in FreeBSD 8.0.
The strcpy
() function is easily misused in
a manner which enables malicious users to arbitrarily change a running
program's functionality through a buffer overflow attack.
February 28, 2009 | macOS 15.2 |