printf()

[Turner, GS \(Geoff\)]

Out of curiosity, why do programmers
insist that the following piece of code
printf("%d", 10);
is wrong and should be
printf("%d\n", 10);

It's application specific, isn't it?

GST

[paulius-maruska]

Turner, GS (Geoff) wrote:

Out of curiosity, why do programmers
insist that the following piece of code
printf("%d", 10);
is wrong and should be
printf("%d\n", 10);

It's application specific, isn't it?

GST

It isn't wrong - it compiles, it links, it runs.
But in real situations, i think there are a lot more cases when
programmers simply forget to put \n, so if you have it in loop (that
should print, say, 20 integers) - output will be realy ugly and you
won't be able to find *what is what* in the output.

[Christopher Benson-Manica]

"Turner, GS \(Geoff\)" <G.********@rl. ac.uk> wrote:

Out of curiosity, why do programmers
insist that the following piece of code
printf("%d", 10);
is wrong and should be
printf("%d\n", 10); It's application specific, isn't it?

Of course. There is, however, at least one situation where it may
very well be Wrong.

#include <stdio.h>

int main( void )
{
printf("%d", 10);
return 0;
}

It is implementation-defined whether the last line of output requires
a newline.

--
Christopher Benson-Manica | I *should* know what I'm talking about - if I
ataru(at)cybers pace.org | don't, I need to know. Flames welcome.

[Kenneth Brody]

paulius-maruska wrote:

Turner, GS (Geoff) wrote:

Out of curiosity, why do programmers
insist that the following piece of code
printf("%d", 10);
is wrong and should be
printf("%d\n", 10);

It's application specific, isn't it?

GST

It isn't wrong - it compiles, it links, it runs.
But in real situations, i think there are a lot more cases when
programmers simply forget to put \n, so if you have it in loop (that
should print, say, 20 integers) - output will be realy ugly and you
won't be able to find *what is what* in the output.

That, and sometimes people give a small sample program to demonstrate
a problem/issue/question, and include a single printf() without the
newline. For example, suppose the above line were the complete body
of main():

#include <stdio.h>
#include <stdlib.h>

int main(void)
{
print("%d",10);
exit(EXIT_SUCCE SS);
}

According to the standard, if the output of the program does not end
in a newline, the output is not guaranteed to appear. (I don't recall
if it's "undefined" or "implementa tion defined".)

--
+-------------------------+--------------------+-----------------------------+
| Kenneth J. Brody | www.hvcomputer.com | |
| kenbrody/at\spamcop.net | www.fptech.com | #include <std_disclaimer .h> |
+-------------------------+--------------------+-----------------------------+
Don't e-mail me at: <mailto:Th***** ********@gmail. com>

[Christopher Benson-Manica]

Kenneth Brody <ke******@spamc op.net> wrote:

According to the standard, if the output of the program does not end
in a newline, the output is not guaranteed to appear. (I don't recall
if it's "undefined" or "implementa tion defined".)

C99 7.19.2:

2 A text stream is an ordered sequence of characters composed
into lines, each line consisting of zero or more characters
plus a terminating new-line character. Whether the last line
requires a terminating new-line character is
implementation-defined.
^^^^^^^^^^^^^^^ ^^^^^^^

(Quoted by Ben Pfaff at http://snipurl.com/iqxx)

--
Christopher Benson-Manica | I *should* know what I'm talking about - if I
ataru(at)cybers pace.org | don't, I need to know. Flames welcome.

[Emmanuel Delahaye]

Turner, GS (Geoff) a écrit :

Out of curiosity, why do programmers
insist that the following piece of code
printf("%d", 10);
is wrong and should be
printf("%d\n", 10);
It's not wrong, it's just that the effect is not portable.

printf("%d", 10);
fflush (stdout);

and

printf("%d\n", 10);

are guaranteed to have the same behaviour whatever the implementation.

It's application specific, isn't it?

Application is irrelevent on c.l.c.

--
C is a sharp tool

[Jirka Klaue]

Emmanuel Delahaye:

printf("%d", 10);
fflush (stdout);

and

printf("%d\n", 10);

are guaranteed to have the same behaviour whatever the implementation.

Did you forget to add: ... except that no new-line is printed by the
first snippet?

Jirka

[Randy Howard]

Emmanuel Delahaye wrote
(in article <43************ **********@news .free.fr>):

Turner, GS (Geoff) a écrit :

Out of curiosity, why do programmers
insist that the following piece of code
printf("%d", 10);
is wrong and should be
printf("%d\n", 10);

It's not wrong, it's just that the effect is not portable.

printf("%d", 10);
fflush (stdout);

and

printf("%d\n", 10);

are guaranteed to have the same behaviour whatever the implementation.

Not the same, but very similar. That newline makes a
difference.
--
Randy Howard (2reply remove FOOBAR)

[Kenneth Brody]

Emmanuel Delahaye wrote:

Turner, GS (Geoff) a écrit :

Out of curiosity, why do programmers
insist that the following piece of code
printf("%d", 10);
is wrong and should be
printf("%d\n", 10);

It's not wrong, it's just that the effect is not portable.

printf("%d", 10);
fflush (stdout);

and

printf("%d\n", 10);

are guaranteed to have the same behaviour whatever the implementation.

[...]

Then I guess I need to get my money back on all these platforms where the
second one outputs a newline that isn't there in the first one.

Not to mention the fact that the missing newline on the first means that
(as I understand it) it is possible that no output appears on some
platforms.

Or did you mean "s/same/different/"?

--
+-------------------------+--------------------+-----------------------------+
| Kenneth J. Brody | www.hvcomputer.com | |
| kenbrody/at\spamcop.net | www.fptech.com | #include <std_disclaimer .h> |
+-------------------------+--------------------+-----------------------------+
Don't e-mail me at: <mailto:Th***** ********@gmail. com>

[Emmanuel Delahaye]

Jirka Klaue a écrit :

Emmanuel Delahaye:

printf("%d", 10);
fflush (stdout);

and

printf("%d\n", 10);

are guaranteed to have the same behaviour whatever the implementation.

Did you forget to add: ... except that no new-line is printed by the
first snippet?

Jirka

No, But when I have reread my post, I have discovered that my intention
was badly worded. I meant that:

On one hand

printf("%d", 10);
fflush (stdout);

and on the other hand

printf("%d\n", 10);

are individually guaranteed to have a well defined and reproductable
behaviour. I don't mean that both have the same behaviour. You are
welcome to rephrase that in plain and simple English.

Thanks
--
C is a sharp tool