using write() instead of puts() in a trivial program?

[Charles Ulrich]

Greetings,

I hope my greenness isn't showing too bad by asking this, but I ran across
this trivial program today that left me flabbergasted:

#define MESSAGE "This account is currently not available.\n"

int
main(int argc, char *argv[])
{
write(STDOUT_FI LENO, MESSAGE, sizeof(MESSAGE) );
_exit(1);
}

This is an excerpt from the newly-rewritten nologin(8) in FreeBSD. I am
not willing to accept that the person who committed this code is a fool,
thus I have to conclude that I just don't understand why exactly the
following isn't good enough for such a trivial program:

puts("This account is currently not available.");

Perhaps write() would be appropriate in a program which did intensive
amounts of output, but the meat of this program is literally 1 line long.

I tried doing a Google search, but as you can imagine, the commonality of
the "write" keyword throws off any results that might be useful, so I was
wondering some kind, generous person here could clue me in on what's going
on here. I'd greatly appreciate it.

Charles Ulrich

[glen herrmannsfeldt]

Keith Thompson wrote:

(snip)

Presumably the FreeBSD nologin program doesn't need to be portable to
anything other than FreeBSD. Given that constraint, I suppose there's
not much advantage in using the portable puts() rather than the
relatively non-portable write(). Having said that, it's not how I would have written it. puts() or
printf() would make for more legible code.

In the days of dynamic link libraries, it is important that some
programs be able to run without dynamic linking. Now, it could
use the static library, but it will be a lot smaller not to.

-- glen

[Dan Pop]

In <pa************ *************** *@BLOODYsecuren ym.SPAMnet> Charles Ulrich <NO***@BLOODYse curenym.SPAMnet > writes:

I hope my greenness isn't showing too bad by asking this, but I ran across
this trivial program today that left me flabbergasted:

#define MESSAGE "This account is currently not available.\n"

int
main(int argc, char *argv[])
{
write(STDOUT_FI LENO, MESSAGE, sizeof(MESSAGE) );
_exit(1);
}

This is an excerpt from the newly-rewritten nologin(8) in FreeBSD. I am
not willing to accept that the person who committed this code is a fool,
thus I have to conclude that I just don't understand why exactly the
following isn't good enough for such a trivial program:

puts("This account is currently not available.");

Perhaps write() would be appropriate in a program which did intensive
amounts of output, but the meat of this program is literally 1 line long.

write() is also appropriate for small programs that are supposed to be
statically linked, while puts() is likely to draw a lot of baggage from
the stdio library. The latter also burns more CPU cycles: in such a
program it is nothing more than a fairly expensive wrapper for a write()
call. The usage of _exit() instead of exit() also indicates a concern
for minimising the number of CPU cycles used by the program, which
explains why the application was not written as a shell script:

#!/bin/sh
echo "This account is currently not available."
exit 1

So, your answer is: the author wanted a standalone application with zero
overhead in terms of disk space and cpu cycles. It's hard to tell whether
his concerns were justified or not, considering that nologin is not even
a standard Unix utility.

Dan
--
Dan Pop
DESY Zeuthen, RZ group
Email: Da*****@ifh.de

[Alan Balmer]

On 12 Jan 2004 23:09:24 GMT, Peteris Krumins
<pk************ ****@inbox.lv> wrote:

I tried doing a Google search, but as you can imagine, the commonality
of the "write" keyword throws off any results that might be useful, so
I was wondering some kind, generous person here could clue me in on
what's going on here. I'd greatly appreciate it.

Charles Ulrich

Finding an answer to such silly problem is the same as asking and trying
to find an answer to a problem like "I have to go to the shop which is
across a street, I chose to go by bike. Maybe I should have chosen to
go to the shop by my shiny car, my shiny helicopter, my elephant?".

Not exactly. In this case, it's "I notice that you took the bike to
the shop rather than the elephant. Was there a reason for that?"

It's a legitimate question, and can provide valuable insight - some of
the best advice a novice can get is "read other people's code." Asking
why a presumably experienced programmer chose one method over another
can be informative and educational. I even consider it topical -
discussing the pros and cons of using standard C rather than the
non-standard write function.

In this case, the best answer is "ask the programmer." Many
open-source programmers are happy to discuss their code. If the OP
wants guesses, my guess would be that the executable using "write" is
smaller with the proper linker options.

--
Al Balmer
Balmer Consulting
re************* ***********@att .net

[Default User]

Alan Balmer wrote:

It's a legitimate question, and can provide valuable insight - some of
the best advice a novice can get is "read other people's code." Asking
why a presumably experienced programmer chose one method over another
can be informative and educational. I even consider it topical -
discussing the pros and cons of using standard C rather than the
non-standard write function.

I'm on the opposite side of that fence, I don't think reading other
people's code is good for newbies. They don't have the experience base
to filter what they are reading. They are far better off sticking with
texts, standards and their own projects until such time as their skills
develop.

Reading code, to me, doesn't really improve programming skills. It
improves the skill of reading code, which is in itself a useful and
important skill if you are going to work in the industry.


Brian Rodenborn

[Alan Balmer]

On Tue, 13 Jan 2004 17:10:47 GMT, Default User
<fi********@boe ing.com.invalid > wrote:

Alan Balmer wrote:

It's a legitimate question, and can provide valuable insight - some of
the best advice a novice can get is "read other people's code." Asking
why a presumably experienced programmer chose one method over another
can be informative and educational. I even consider it topical -
discussing the pros and cons of using standard C rather than the
non-standard write function.

I'm on the opposite side of that fence, I don't think reading other
people's code is good for newbies. They don't have the experience base
to filter what they are reading.

Which is why they come here to ask ;-)
They are far better off sticking with
texts,
Texts are not necessarily a source of good programming practices. Many
of the popular ones misinform.
standards
I may be wrong, but I don't see the standard as being useful for new
programmers. Once "how" turns into "why" and "why not", the standard
is good, but that requires some experience.
and their own projects until such time as their skills
develop.
That's probably the best, *providing* they get proper feedback.
Otherwise, just developing their own projects can do more harm than
good.
Reading code, to me, doesn't really improve programming skills. It
improves the skill of reading code, which is in itself a useful and
important skill if you are going to work in the industry.
If I don't know how to do something, and I read someone else's code
which does it, it improves my programming skills.

I think reading *good* code is educational. Maybe we need an
"approved" body of reading material <g>. It may well be that random
bits of BSD source code don't qualify.

--
Al Balmer
Balmer Consulting
re************* ***********@att .net

[Dan Pop]

In <40************ ***@boeing.com. invalid> Default User <fi********@boe ing.com.invalid > writes:

Reading code, to me, doesn't really improve programming skills. It
improves the skill of reading code, which is in itself a useful and
important skill if you are going to work in the industry.

Reading well written code does improve programming skills, because you
get to learn better ways of doing certain things.

Dan
--
Dan Pop
DESY Zeuthen, RZ group
Email: Da*****@ifh.de

[Richard Heathfield]

Alan Balmer wrote:

On 12 Jan 2004 23:09:24 GMT, Peteris Krumins
<pk************ ****@inbox.lv> wrote:

Finding an answer to such silly problem is the same as asking and trying
to find an answer to a problem like "I have to go to the shop which is
across a street, I chose to go by bike. Maybe I should have chosen to
go to the shop by my shiny car, my shiny helicopter, my elephant?".

Not exactly. In this case, it's "I notice that you took the bike to
the shop rather than the elephant. Was there a reason for that?"

Don't be silly. Why would anyone take a bike to an elephant?

<g,d&r>

--
Richard Heathfield : bi****@eton.pow ernet.co.uk
"Usenet is a strange place." - Dennis M Ritchie, 29 July 1999.
C FAQ: http://www.eskimo.com/~scs/C-faq/top.html
K&R answers, C books, etc: http://users.powernet.co.uk/eton

[Default User]

Dan Pop wrote:

In <40************ ***@boeing.com. invalid> Default User <fi********@boe ing.com.invalid > writes:

Reading code, to me, doesn't really improve programming skills. It
improves the skill of reading code, which is in itself a useful and
important skill if you are going to work in the industry.

Reading well written code does improve programming skills, because you
get to learn better ways of doing certain things.

But that usually requires a sufficient skill level to be able to take
advantage of the new knowledge. Newbies can't tell good code from bad,
good practices from crap, nifty new techniques from hacky, unsafe
shortcuts. It also encourages cut-n-paste cargo cultism.


Brian Rodenborn

[CBFalconer]

Richard Heathfield wrote:

Alan Balmer wrote:

<pk************ ****@inbox.lv> wrote:

Finding an answer to such silly problem is the same as asking
and trying to find an answer to a problem like "I have to go
to the shop which is across a street, I chose to go by bike.
Maybe I should have chosen to go to the shop by my shiny car,
my shiny helicopter, my elephant?".

Not exactly. In this case, it's "I notice that you took the
bike to the shop rather than the elephant. Was there a reason
for that?"

Don't be silly. Why would anyone take a bike to an elephant?

So the elephant could learn to ride it, and make than 'anyone' a
pot of money in the circus.

<d & r II>

--
Chuck F (cb********@yah oo.com) (cb********@wor ldnet.att.net)
Available for consulting/temporary embedded and systems.
<http://cbfalconer.home .att.net> USE worldnet address!

[Dan Pop]

In <40************ ***@boeing.com. invalid> Default User <fi********@boe ing.com.invalid > writes:

Dan Pop wrote:

In <40************ ***@boeing.com. invalid> Default User <fi********@boe ing.com.invalid > writes:

>Reading code, to me, doesn't really improve programming skills. It ^^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^^ ^^^^^^^^^^^ >improves the skill of reading code, which is in itself a useful and
>important skill if you are going to work in the industry.
Reading well written code does improve programming skills, because you ^^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^^ ^ get to learn better ways of doing certain things.

But that usually requires a sufficient skill level to be able to take
advantage of the new knowledge.

We're talking about *improving* programming skills, not about *acquiring*
them, right?
Newbies can't tell good code from bad,
good practices from crap, nifty new techniques from hacky, unsafe
shortcuts.
Newbies can ask advanced programmers for pieces of good C code, that
can be used for this purpose. Few people are learning C alone on a
desert island...
It also encourages cut-n-paste cargo cultism.

Not in my experience. The main purpose of the exercise is to get ideas
about how to code in C, rather than finding solutions to a concrete
problem. For the latter, people usually go to algorithms books with
examples in C.

Dan
--
Dan Pop
DESY Zeuthen, RZ group
Email: Da*****@ifh.de