STRCPY(3)

NAME
strcpy, strncpy - copy strings

LIBRARY
libc

SYNOPSIS
#include <string.h>
char *
stpcpy(char *dst, const char *src);
char *
strcpy(char * restrict dst, const char * restrict src);
char *
strncpy(char * restrict dst, const char * restrict src, size_t len);

DESCRIPTION
The stpcpy() and strcpy() functions copy the string src to dst (including the terminating ‘\0’ character.)

The strncpy() function copies 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.

RETURN VALUES
The strcpy() and strncpy() functions return dst. The stpcpy() function returns a pointer to the terminating ‘\0’ character of dst.

EXAMPLES
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.

SECURITY CONSIDERATIONS
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. (See the FSA and EXAMPLES.)

SEE ALSO
bcopy(3), memccpy(3), memcpy(3), memmove(3), strlcpy(3) The FreeBSD Security Architecture. (See /usr/share/doc/{to be decided}.)

STANDARDS
The strcpy() and strncpy() functions conform to isoC. The stpcpy() function is an MS-DOS and GNUism. The stpcpy() function conforms to no standard.

HISTORY
The stpcpy() function first appeared in FreeBSD 4.4, coming from 1998-vintage Linux.