char* strcpy( char* dest, const char* src );
(until C99)char* strcpy( char* restrict dest, const char* restrict src );
(since C99)errno_t strcpy_s( char* restrict dest, rsize_t destsz, const char* restrict src );
(2) (since C11)1) Copies the null-terminated byte string pointed to by src, including the null terminator, to the character array whose first element is pointed to by dest.
The behavior is undefined if the dest array is not large enough. The behavior is undefined if the strings overlap. The behavior is undefined if either dest is not a pointer to a character array or src is not a pointer to a null-terminated byte string.
2)Same as
(1), except that it may clobber the rest of the destination array with unspecified values and that the following errors are detected at runtime and call the currently installed
constraint handlerfunction:
The behavior is undefined if the size of the character array pointed to by
dest <= strnlen_s(src, destsz) < destsz; in other words, an erroneous value of
destszmay permit buffer overflow.
strcpy_s is only guaranteed to be available if __STDC_LIB_EXT1__ is defined by the implementation and if the user defines __STDC_WANT_LIB_EXT1__ to the integer constant 1 before including <string.h>.
1) returns a copy of dest
2) returns zero on success, returns non-zero on error. Also, on error, writes zero to dest[0] (unless dest is a null pointer or destsz is zero or greater than RSIZE_MAX).
[edit] Notesstrcpy_s is allowed to clobber the destination array from the last character written up to destsz in order to improve efficiency: it may copy in multibyte blocks and then check for null bytes.
The function strcpy_s is similar to the BSD function strlcpy, except that
strlcpy truncates the source string to fit in the destination (which is a security risk)strlcpy does not perform all the runtime checks that strcpy_s doesstrlcpy does not make failures obvious by setting the destination to a null string or calling a handler if the call fails.Although strcpy_s prohibits truncation due to potential security risks, it's possible to truncate a string using bounds-checked strncpy_s instead.
#define __STDC_WANT_LIB_EXT1__ 1
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int main(void)
{
const char* src = "Take the test.";
// src[0] = 'M' ; // this would be undefined behavior
char dst[strlen(src) + 1]; // +1 to accommodate for the null terminator
strcpy(dst, src);
dst[0] = 'M'; // OK
printf("src = %s\ndst = %s\n", src, dst);
#ifdef __STDC_LIB_EXT1__
set_constraint_handler_s(ignore_handler_s);
int r = strcpy_s(dst, sizeof dst, src);
printf("dst = \"%s\", r = %d\n", dst, r);
r = strcpy_s(dst, sizeof dst, "Take even more tests.");
printf("dst = \"%s\", r = %d\n", dst, r);
#endif
}
Possible output:
src = Take the test. dst = Make the test. dst = "Take the test.", r = 0 dst = "", r = 22[edit] References
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