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@(#)strcpy.3 8.1 (Berkeley) 6/4/93
$FreeBSD: releng/11.0/lib/libc/string/strcpy.3 262890 2014-03-07 15:35:54Z eadler $
.Dd February 28, 2009 .Dt STRCPY 3 .Os .Sh NAME .Nm stpcpy, stpncpy, strcpy , strncpy .Nd copy strings .Sh LIBRARY .Lb libc .Sh SYNOPSIS n string.h .Ft char * .Fn stpcpy "char * restrict dst" "const char * restrict src" .Ft char * .Fn stpncpy "char * restrict dst" "const char * restrict src" "size_t len" .Ft char * .Fn strcpy "char * restrict dst" "const char * restrict src" .Ft char * .Fn strncpy "char * restrict dst" "const char * restrict src" "size_t len" .Sh DESCRIPTION The .Fn stpcpy and .Fn strcpy functions copy the string .Fa src to .Fa dst (including the terminating .Ql \e0 character.)
p The .Fn stpncpy and .Fn strncpy functions copy at most .Fa len characters from .Fa src into .Fa dst . If .Fa src is less than .Fa len characters long, the remainder of .Fa dst is filled with .Ql \e0 characters. Otherwise, .Fa dst is .Em not terminated. .Sh RETURN VALUES The .Fn strcpy and .Fn strncpy functions return .Fa dst . The .Fn stpcpy and .Fn stpncpy functions return a pointer to the terminating .Ql \e0 character of .Fa dst . If .Fn stpncpy does not terminate .Fa dst with a .Dv NUL character, it instead returns a pointer to .Li dst[n] (which does not necessarily refer to a valid memory location.) .Sh EXAMPLES The following sets .Va chararray to .Dq Li abc\e0\e0\e0 : d -literal -offset indent char chararray[6]; (void)strncpy(chararray, "abc", sizeof(chararray)); .Ed
p The following sets .Va chararray to .Dq Li abcdef : d -literal -offset indent char chararray[6]; (void)strncpy(chararray, "abcdefgh", sizeof(chararray)); .Ed
p Note that it does .Em not .Tn NUL terminate .Va chararray because the length of the source string is greater than or equal to the length argument.
p The following copies as many characters from .Va input to .Va buf as will fit and .Tn NUL terminates the result. Because .Fn strncpy does .Em not guarantee to .Tn NUL terminate the string itself, this must be done explicitly. d -literal -offset indent char buf[1024]; (void)strncpy(buf, input, sizeof(buf) - 1); buf[sizeof(buf) - 1] = '\e0'; .Ed
p This could be better achieved using .Xr strlcpy 3 , as shown in the following example:
p .Dl "(void)strlcpy(buf, input, sizeof(buf));"
p Note that because .Xr strlcpy 3 is not defined in any standards, it should only be used when portability is not a concern. .Sh SEE ALSO .Xr bcopy 3 , .Xr memccpy 3 , .Xr memcpy 3 , .Xr memmove 3 , .Xr strlcpy 3 , .Xr wcscpy 3 .Sh STANDARDS The .Fn strcpy and .Fn strncpy functions conform to .St -isoC . The .Fn stpcpy and .Fn stpncpy functions conform to .St -p1003.1-2008 . .Sh HISTORY The .Fn stpcpy function first appeared in .Fx 4.4 , and .Fn stpncpy was added in .Fx 8.0 . .Sh SECURITY CONSIDERATIONS The .Fn 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.