NAME
strcpy, strncpy - copy a string
SYNOPSIS
#include <string.h>
I char *strcpy(char * dest , const char * src );
I char *strncpy(char * dest , const char * src , size_t n );
DESCRIPTION
The
R strcpy ()
function copies the string pointed to by src,
including the terminating null byte ('\0'),
to the buffer pointed to by dest.
The strings may not overlap, and the destination string
dest must be large enough to receive the copy.
The
R strncpy ()
function is similar, except that at most
n bytes of src are copied.
R Warning :
If there is no null byte
among the first n bytes of src,
the string placed in dest will not be null terminated.
If the length of
src
is less than
R n ,
R strncpy ()
pads the remainder of
dest
with null bytes.
A simple implementation of
R strncpy ()
might be:
char*
strncpy(char *dest, const char *src, size_t n){
size_t i;
for (i = 0 ; i < n && src[i] != '\0' ; i++)
dest[i] = src[i];
for ( ; i < n ; i++)
dest[i] = '\0';
return dest;
}
RETURN VALUE
The
R strcpy ()
and
R strncpy ()
functions return a pointer to
the destination string dest.
CONFORMING TO
SVr4, 4.3BSD, C89, C99.
NOTES
Some programmers consider
R strncpy ()
to be inefficient and error prone.
If the programmer knows (i.e., includes code to test!)
that the size of
dest is greater than
the length of
src, then
R strcpy ()
can be used.
If there is no terminating null byte in the first
n
characters of
src,
R strncpy ()
produces an unterminated string in
dest.
Programmers often prevent this mistake by forcing termination
as follows:
strncpy(buf, str, n);
if (n > 0)
buf[n - 1]= '\0';
BUGS
If the destination string of a
R strcpy ()
is not large enough
(that is, if the programmer was stupid or lazy, and failed to check
the size before copying) then anything might happen.
Overflowing fixed length strings is a favorite cracker technique.
SEE ALSO
ČLÁNKY DO MAILU