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STRCPY(3)                  Linux Programmer's Manual                 STRCPY(3)



NAME
       strcpy, strncpy - copy a string

SYNOPSIS
       #include <&lt;string.h>&gt;

       char *strcpy(char *dest, const char *src);

       char *strncpy(char *dest, const char *src, size_t n);

DESCRIPTION
       The  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 strncpy() function is similar, except that at most n bytes  of  src
       are  copied.  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 n, strncpy() pads  the  remainder  of
       dest with null bytes.

       A simple implementation of 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  strcpy()  and strncpy() functions return a pointer to the destina-
       tion string dest.

CONFORMING TO
       SVr4, 4.3BSD, C89, C99.

NOTES
       Some programmers consider 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 strcpy() can be used.

       If there is no terminating null byte in the first n characters of  src,
       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 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
       bcopy(3), memccpy(3), memcpy(3), memmove(3), wcscpy(3), wcsncpy(3)

COLOPHON
       This  page  is  part of release 3.05 of the Linux man-pages project.  A
       description of the project, and information about reporting  bugs,  can
       be found at http://www.kernel.org/doc/man-pages/.



GNU                               2007-06-15                         STRCPY(3)