Prop. page man strncpy V2

Voici donc, après vos nombreuses remarques, une nouvelle version de
proposition de page man pour strcpy et strncpy


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

NAME
strcpy, strncpy - copy a string

SYNOPSIS
#include <string.h>

C89
char *strcpy(char *dest, const char *src);

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

C99
char *strcpy(char *restrict dest, const char *restrict src);

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

DESCRIPTION
The strcpy() function copies the string pointed to by src (including
the terminating `\0' character) to the array 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
- not more than n bytes of src are copied,
- src could be not null-terminated.
Thus, if there is no null byte among the first n bytes of src, dest will
not be null-terminated.

In the case where the length of src is less than n, the remainder of
dest will be padded with nulls.

Assuming that src is null-terminated, a (very poor quality)
implementation of strncpy() could be

char*
optimist_strncpy(char *restrict dest, const char *restrict src, size_t n){
if (n != 0) {
size_t src_len= strlen(src); // BUG if src not null-terminated
size_t i;

for(i=0 ; i < src_len && i < n; i++)
dest[i]= src[i];
for( ; i < n ; i++)
dest[i]= '\0';
}

return dest;
}

Another (poor quality but conform) implementation of strncpy() could be:

char*
strncpy(char *restrict dest, const char *restrict 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.

BUGS
If the destination string of a strcpy() is not large enough (that is,
if the programmer was stupid/lazy, and failed to check the size before
copying) then anything might happen. Overflowing fixed length strings
is a favourite cracker technique.

A common mistake with strncpy() is to forget that it, if
strlen(src) >= n, then, the '\0' termination character is not set.

NOTE
Some programmers consider strncpy() as inefficient and error
prone. If the programmer knows the the size of dest is greater than
the length of src, then, strcpy() can be used. Otherwise, using
strncpy() makes a non null terminated string.

Programmers often prevent this mistake by forcing '\0' termination
this way:

strncpy(buf, str, n);
if (n) buf[n - 1]= '\0';

If n can not be nul, the test can be removed.


CONFORMING TO
SVID 3, POSIX, BSD 4.3, ISO 9899

SEE ALSO
bcopy(3), memccpy(3), memcpy(3), memmove(3), wcscpy(3), wcsncpy(3)

GNU 1993-04-11 STRCPY(3)

--
Je ne respecte plus le code de la route à vélo depuis une double fracture
due au fait que j'étais le seul à le respecter.