fread/fwrite

[empriser]

How to use fread/fwrite copy a file.
When reach file's end, fread return 0, I don't konw how many bytes
in buf.

[Guru Jois]

On Jul 5, 6:42 pm, Peter Nilsson <[e-mail]. auwrote:

Eric Sosman <[e-mail] e:

empriser wrote:

...
Yes my buffer size is n (n 1).
How do I know there are how many bytes in buffer,
after last call fread as if return 0.

fread returns the number of elements that were
read and stored in the buffer. If fread returns 10,
it successfully read and stored 10 elements. If
fread returns 0, it read and stored ... <wait for
it... no elements.

In other words, code as...

static char buf[1024];
size_t r = fread(buf, 1, sizeof buf, fp);

...rather than...

static char buf[1024];
size_t r = fread(buf, sizeof buf, 1, fp);

Assuming no read errors, if there are 123 characters
left in the stream, the former will return 0 into r,
whereas the latter will return 123. Both calls will
read the same number of characters though.

--
Peter

Is size_t and all such stuffs portable in c? If not what to make it
so?
Guru Jois

[santosh]

Guru Jois wrote:

On Jul 5, 6:42 pm, Peter Nilsson <[e-mail]. auwrote:

Eric Sosman <[e-mail] e:

empriser wrote:
...
Yes my buffer size is n (n 1).
How do I know there are how many bytes in buffer,
after last call fread as if return 0.

fread returns the number of elements that were
read and stored in the buffer. If fread returns 10,
it successfully read and stored 10 elements. If
fread returns 0, it read and stored ... <wait for
it... no elements.

In other words, code as...

static char buf[1024];
size_t r = fread(buf, 1, sizeof buf, fp);

...rather than...

static char buf[1024];
size_t r = fread(buf, sizeof buf, 1, fp);

Assuming no read errors, if there are 123 characters
left in the stream, the former will return 0 into r,
whereas the latter will return 123. Both calls will
read the same number of characters though.

Is size_t and all such stuffs portable in c? If not what to make it
so?

size_t is defined in the Standard, so it's certainly portable. New
users to C tend to have some confusion over using size_t objects with
printf and family. Generally using the lu format specifier with a cast
to the appropriate type is recommended. If you can, and want to, use
C99's additions the zu specifier is specifically there for size_t.

[CBFalconer]

Guru Jois wrote:

>

.... snip ...

>
Is size_t and all such stuffs portable in c? If not what to make
it so?

Yes. That is, in part, why this newsgroup limits the topic to
STANDARD C, and considers references to system dependent things as
being off-topic. Read the standard.

--
<http://www.cs.auckland .ac.nz/~pgut001/pubs/vista_cost.txt>
<http://www.securityfoc us.com/columnists/423>
<http://www.aaxnet.com/editor/edit043.html>
cbfalconer at maineline dot net

--
Posted via a free Usenet account from http://www.teranews.com

[Guru Jois]

On Jul 8, 4:03 am, CBFalconer <cbfalco...@yah oo.comwrote:

Guru Jois wrote:

... snip ...

Is size_t and all such stuffs portable in c? If not what to make
it so?

Yes. That is, in part, why this newsgroup limits the topic to
STANDARD C, and considers references to system dependent things as
being off-topic. Read the standard.

--
<http://www.cs.auckland .ac.nz/~pgut001/pubs/vista_cost.txt>
<http://www.securityfoc us.com/columnists/423>
<http://www.aaxnet.com/editor/edit043.html>
cbfalconer at maineline dot net

--
Posted via a free Usenet account fromhttp://www.teranews.co m

How and where can I read to understand the perfect knowledge about C
standards.
Any docs/links to learn pure portable programs for C??? Docs
prefered..

Guru Jois

[santosh]

Guru Jois wrote:

On Jul 8, 4:03 am, CBFalconer <cbfalco...@yah oo.comwrote:

Guru Jois wrote:

... snip ...

Is size_t and all such stuffs portable in c? If not what to make
it so?

Yes. That is, in part, why this newsgroup limits the topic to
STANDARD C, and considers references to system dependent things as
being off-topic. Read the standard.

How and where can I read to understand the perfect knowledge about C
standards.
Any docs/links to learn pure portable programs for C??? Docs
prefered..

As far as online tutorials are concerned I'll recommend Steve Summit's
one:

<http://www.eskimo.com/~scs/cclass/>

Also he maintains the very useful C FAQ:

<http://www.c-faq.com/>

There's also a clc "wiki":

<http://clc-wiki.net/>

Other resources include:

<http://www.lysator.liu .se/c/>
<http://www.dinkumware. com/manuals/>
<http://www-ccs.ucsd.edu/c/>
<http://www.open-std.org/jtc1/sc22/wg14/ - Site for the draft
Standard.
<http://www.knosof.co.u k/cbook/cbook.html>
<http://www.cpax.org.uk/prg/portable/c/index.php>

[Richard Heathfield]

santosh said:

<snip>

As far as online tutorials are concerned I'll recommend Steve Summit's
one:

<http://www.eskimo.com/~scs/cclass/>

Please allow me to add the Tom Torfs tutorial URL:

<http://cprog.tomsweb.n et/cintro.html>

Tom used to be a regular (and highly respected) comp.lang.c contributor.
Then, one day, he asked a question about C99, and it transpired that he
was writing a C99 preprocessor. He has not been seen since.

--
Richard Heathfield <http://www.cpax.org.uk >
Email: -www. +rjh@
Google users: <http://www.cpax.org.uk/prg/writings/googly.php>
"Usenet is a strange place" - dmr 29 July 1999

[¬a\\/b]

On Sun, 08 Jul 2007 02:36:55 -0700, santosh wrote:

>Guru Jois wrote:

>On Jul 5, 6:42 pm, Peter Nilsson <[e-mail]. auwrote:

Eric Sosman <[e-mail] e:
empriser wrote:
...
Yes my buffer size is n (n 1).
How do I know there are how many bytes in buffer,
after last call fread as if return 0.

fread returns the number of elements that were
read and stored in the buffer. If fread returns 10,
it successfully read and stored 10 elements. If
fread returns 0, it read and stored ... <wait for
it... no elements.

In other words, code as...

static char buf[1024];
size_t r = fread(buf, 1, sizeof buf, fp);

...rather than...

static char buf[1024];
size_t r = fread(buf, sizeof buf, 1, fp);

Assuming no read errors, if there are 123 characters
left in the stream, the former will return 0 into r,
whereas the latter will return 123. Both calls will
read the same number of characters though.

Is size_t and all such stuffs portable in c? If not what to make it
so?

size_t is defined in the Standard, so it's certainly portable. New
users to C tend to have some confusion over using size_t objects with
printf and family. Generally using the lu format specifier with a cast
to the appropriate type is recommended. If you can, and want to, use
C99's additions the zu specifier is specifically there for size_t.

size_t is not portable because you all don't know the size it has
only uint8_t uint16_t uint32_t, uint64_t are portable

[Richard Heathfield]

¬a\/b said:

On Sun, 08 Jul 2007 02:36:55 -0700, santosh wrote:

<snip>

>>size_t is defined in the Standard, so it's certainly portable. New
users to C tend to have some confusion over using size_t objects with
printf and family. Generally using the lu format specifier with a cast
to the appropriate type is recommended. If you can, and want to, use
C99's additions the zu specifier is specifically there for size_t.

size_t is not portable because you all don't know the size it has

Nonsense. It is exactly sizeof(size_t) bytes in size.

only uint8_t uint16_t uint32_t, uint64_t are portable

My implementation has never heard of them, and gives me compilation
errors when I try to use them. So much for "portable".

But my implementation understands size_t just fine, thanks.

--
Richard Heathfield <http://www.cpax.org.uk >
Email: -www. +rjh@
Google users: <http://www.cpax.org.uk/prg/writings/googly.php>
"Usenet is a strange place" - dmr 29 July 1999

[Flash Gordon]

¬a\/b wrote, On 09/07/07 07:42:

On Sun, 08 Jul 2007 02:36:55 -0700, santosh wrote:

>Guru Jois wrote:

>>On Jul 5, 6:42 pm, Peter Nilsson <[e-mail]. auwrote:
Eric Sosman <[e-mail] e:
empriser wrote:
>...
>Yes my buffer size is n (n 1).
>How do I know there are how many bytes in buffer,
>after last call fread as if return 0.
fread returns the number of elements that were
read and stored in the buffer. If fread returns 10,
it successfully read and stored 10 elements. If
fread returns 0, it read and stored ... <wait for
it... no elements.
In other words, code as...

static char buf[1024];
size_t r = fread(buf, 1, sizeof buf, fp);

...rather than...

static char buf[1024];
size_t r = fread(buf, sizeof buf, 1, fp);

Assuming no read errors, if there are 123 characters
left in the stream, the former will return 0 into r,
whereas the latter will return 123. Both calls will
read the same number of characters though.
Is size_t and all such stuffs portable in c? If not what to make it
so?

size_t is defined in the Standard, so it's certainly portable. New
users to C tend to have some confusion over using size_t objects with
printf and family. Generally using the lu format specifier with a cast
to the appropriate type is recommended. If you can, and want to, use
C99's additions the zu specifier is specifically there for size_t.

size_t is not portable because you all don't know the size it has
only uint8_t uint16_t uint32_t, uint64_t are portable

Rubbish. There is no guarantee that the types you are suggesting are
available (even assuming C99) so they are less portable than size_t
which is *guaranteed* to exist. size_t is also the type returned by
fread (the function being called above), so whatever it is a variable of
type size_t is *guaranteed* to be large enough.
--
Flash Gordon

[¬a\\/b]

On Mon, 09 Jul 2007 08:19:40 +0100, Flash Gordon
<sp**@flash-gordon.me.ukwro te:

>¬a\/b wrote, On 09/07/07 07:42:

>On Sun, 08 Jul 2007 02:36:55 -0700, santosh wrote:

>>Guru Jois wrote:
On Jul 5, 6:42 pm, Peter Nilsson <[e-mail]. auwrote:
Eric Sosman <[e-mail] e:
>empriser wrote:
>>...
>>Yes my buffer size is n (n 1).
>>How do I know there are how many bytes in buffer,
>>after last call fread as if return 0.
> fread returns the number of elements that were
>read and stored in the buffer. If fread returns 10,
>it successfully read and stored 10 elements. If
>fread returns 0, it read and stored ... <wait for
>it... no elements.
In other words, code as...
>
static char buf[1024];
size_t r = fread(buf, 1, sizeof buf, fp);
>
...rather than...
>
static char buf[1024];
size_t r = fread(buf, sizeof buf, 1, fp);
>
Assuming no read errors, if there are 123 characters
left in the stream, the former will return 0 into r,
whereas the latter will return 123. Both calls will
read the same number of characters though.
Is size_t and all such stuffs portable in c? If not what to make it
so?
size_t is defined in the Standard, so it's certainly portable. New
users to C tend to have some confusion over using size_t objects with
printf and family. Generally using the lu format specifier with a cast
to the appropriate type is recommended. If you can, and want to, use
C99's additions the zu specifier is specifically there for size_t.

size_t is not portable because you all don't know the size it has
only uint8_t uint16_t uint32_t, uint64_t are portable

Rubbish. There is no guarantee that the types you are suggesting are
available (even assuming C99) so they are less portable than size_t
which is *guaranteed* to exist. size_t is also the type returned by
fread (the function being called above), so whatever it is a variable of
type size_t is *guaranteed* to be large enough.

each data definition that not fixed the size is unportable
each operation to data operand not well definited is unportable