strncpy(3) [suse man page]

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

NAME

       strcpy, strncpy - copy a string

SYNOPSIS

       #include <string.h>

       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 (''), 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] != '' ; i++)
		   dest[i] = src[i];
	       for ( ; i < n ; i++)
		   dest[i] = '';

	       return dest;
	   }

RETURN VALUE

       The strcpy() and strncpy() functions return a pointer to the destination 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]= '';

BUGS

       If  the	destination  string  of  a strcpy() is not large enough, then anything might happen.  Overflowing fixed-length string buffers is a
       favorite cracker technique for taking complete control of the machine.  Any time a program reads or copies data into a buffer, the  program
       first  needs to check that there's enough space.  This may be unnecessary if you can show that overflow is impossible, but be careful: pro-
       grams can get changed over time, in ways that may make the impossible possible.

SEE ALSO

       bcopy(3), memccpy(3), memcpy(3), memmove(3), stpcpy(3), strdup(3), wcscpy(3), wcsncpy(3)

COLOPHON

       This page is part of release 3.25 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
								    2009-12-04								 STRCPY(3)

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

NAME

       strcpy, strncpy - copy a string

SYNOPSIS

       #include <string.h>

       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 (''), 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] != '' ; i++)
		   dest[i] = src[i];
	       for ( ; i < n ; i++)
		   dest[i] = '';

	       return dest;
	   }

RETURN VALUE

       The strcpy() and strncpy() functions return a pointer to the destination 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]= '';

BUGS

       If  the	destination  string  of  a strcpy() is not large enough, then anything might happen.  Overflowing fixed-length string buffers is a
       favorite cracker technique for taking complete control of the machine.  Any time a program reads or copies data into a buffer, the  program
       first  needs to check that there's enough space.  This may be unnecessary if you can show that overflow is impossible, but be careful: pro-
       grams can get changed over time, in ways that may make the impossible possible.

SEE ALSO

       bcopy(3), memccpy(3), memcpy(3), memmove(3), stpcpy(3), strdup(3), wcscpy(3), wcsncpy(3)

COLOPHON

       This page is part of release 3.25 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
								    2009-12-04								 STRCPY(3)