Unix C programming for finding file

**dandelion** · Nov 14 '05, 03:41 PM

[OT] Re: Unix C programming for finding file

"dawn" <ming@lian.co m> wrote in message
news:30jp61F31b de9U1@uni-berlin.de...[color=blue]
> Hi all,
> I am now working on a C program under Unix.
> The requirement for the program is that:
> A file name is passed to program as a parameter. The program will
> Find files under a specified directory. The matched file must have the
> same content with the given file. It does not matter whether the
> filenames are the same.
>
> It is easy to find file that has the same name with given file, but
> may be hard to find the files that with the same content. In my
> knowledge, i give two solutions:
>
> 1) Go throught the directory and its sub direcotry tree, and when
> meeting a file, Use the stand C library function to open that file and
> the given file, and then compare those contents in buffers to see if
> they are the same.
>
> 2) Go through the directory and its sub deirectroy tree, and when
> meeting a file, execute the system shell command "diff" to compare the
> two files to see if they are the same in content.
>
>
> The two solutions seems not very smart and they are very running
> slowly. I wonder if there is any library function that can compare two
> file contents just like "strcmp" to compare two string.
> Or maybe there are some other smart ways to achieve it.
>
> Thank you for suggestions.[/color]

I'm pretty sure there isn't one.

<OT>
A few things spring to mind, though.

A) if you are going to use a shell cmd, try 'cmp' instead of diff. It
handles binary files, too *and* it's
faster.

B) if speed is important, try to improve it by doing a 'stat()' and compare
files-size. If the size is
different, the two files cannot be the same.

C) if you *must* compare actual files, use fread to read entire blocks and
do the comparison in
memory. Allocate relative large blocks and end on the first actual
difference.

</OT>

**Charlie Gordon** · Nov 14 '05, 03:41 PM

Re: Unix C programming for finding file

"dawn" <ming@lian.co m> wrote in message news:30jp61F31b de9U1@uni-berlin.de...[color=blue]
> Hi all,
> I am now working on a C program under Unix. [...][/color]

There is no support for enumerating directory contents in standard C, you should
seek help on a unix newsgroup or pull the man pages for opendir(), readdir(),
closedir() and related APIs.

--
Chqrlie.

**Dan Pop** · Nov 14 '05, 03:41 PM

Re: Unix C programming for finding file

In <30jp61F31bde9U 1@uni-berlin.de> dawn <ming@lian.co m> writes:
[color=blue]
> I am now working on a C program under Unix.[/color]

And you're too stupid to realise that comp.unix.progr ammer is the right
place for your question.
[color=blue]
> The requirement for the program is that:
> A file name is passed to program as a parameter. The program will
>Find files under a specified directory. The matched file must have the
>same content with the given file. It does not matter whether the
>filenames are the same.[/color]

Standard C provides no support for directories, which is why posting to
comp.lang.c was such a silly thing.
[color=blue]
> It is easy to find file that has the same name with given file, but
>may be hard to find the files that with the same content. In my
>knowledge, i give two solutions:
>
> 1) Go throught the directory and its sub direcotry tree, and when
>meeting a file, Use the stand C library function to open that file and
>the given file, and then compare those contents in buffers to see if
>they are the same.[/color]

The Unix function ftw() does most of the job for you. You only have to
provide a function for comparing the contents of the two files and such
a function is damn fast if you do it right: compare the contents only
if the files have the same size, use fread() and memcmp() to perform the
comparison on BUFSIZ sized chunks. Note that ftw is giving you the stat
info about each directory entry, so you don't have to do anything special
in order to obtain the file size.

For extra points, lock *at least* the reference file, to be sure that its
contents is stable during the program execution. But don't ask here how!

Dan
--
Dan Pop
DESY Zeuthen, RZ group
Email: Dan.Pop@ifh.de
Currently looking for a job in the European Union

**fallujahdestrotedbyusbastards@peace.com** · Nov 14 '05, 03:43 PM

Re: Unix C programming for finding file

On 24 Nov 2004 17:00:35 GMT, Dan.Pop@cern.ch (Dan Pop) wrote:
[color=blue]
>In <30jp61F31bde9U 1@uni-berlin.de> dawn <ming@lian.co m> writes:
>[color=green]
>> I am now working on a C program under Unix.[/color]
>
>And you're too stupid to realise that comp.unix.progr ammer is the right
>place for your question.
>[/color]
You unbelieveably ignorant arsehole. He is writing a C program
therefore this is exactly the right place to ask his question.
Are you a yank ?

**Mark McIntyre** · Nov 14 '05, 03:43 PM

Re: Unix C programming for finding file

On Thu, 25 Nov 2004 21:20:55 +0000, in comp.lang.c ,
fallujahdestrot edbyusbastards@ peace.com wrote:
[color=blue]
>On 24 Nov 2004 17:00:35 GMT, Dan.Pop@cern.ch (Dan Pop) wrote:
>[color=green]
>>In <30jp61F31bde9U 1@uni-berlin.de> dawn <ming@lian.co m> writes:
>>[color=darkred]
>>> I am now working on a C program under Unix.[/color]
>>
>>And you're too stupid to realise that comp.unix.progr ammer is the right
>>place for your question.
>>[/color]
>You unbelieveably ignorant arsehole. He is writing a C program
>therefore this is exactly the right place to ask his question.[/color]

Not if the question relates to unix features. C is not unix. Since between
you adn Dan you snipped the entire original posting, its not possible to
say now.
[color=blue]
>Are you a yank ?[/color]

Dan is swiss or german, and one of the serious experts round here, if
lacking in much social grace.

But don't let that stop you ranting mindlessly.

--
Mark McIntyre
CLC FAQ <http://www.eskimo.com/~scs/C-faq/top.html>
CLC readme: <http://www.ungerhu.com/jxh/clc.welcome.txt >

**Jens.Toerring@physik.fu-berlin.de** · Nov 14 '05, 03:43 PM

Re: Unix C programming for finding file

fallujahdestrot edbyusbastards@ peace.com wrote:[color=blue]
> On 24 Nov 2004 17:00:35 GMT, Dan.Pop@cern.ch (Dan Pop) wrote:[/color]
[color=blue][color=green]
>>In <30jp61F31bde9U 1@uni-berlin.de> dawn <ming@lian.co m> writes:
>>[color=darkred]
>>> I am now working on a C program under Unix.[/color]
>>
>>And you're too stupid to realise that comp.unix.progr ammer is the right
>>place for your question.
>>[/color]
> You unbelieveably ignorant arsehole.[/color]

And what are you just proving to be? Let's see...
[color=blue]
> He is writing a C program
> therefore this is exactly the right place to ask his question.[/color]

No, he isn't right here. Would you do the absolute minimum of reading
a few posts in the group before jumping in you would know very well
that discussions about platform specific extensions to C is off-topic
here. So far about your claim about Dan's "ignorance" . Looks a lot
more like it's the other way round. And Dan even went so far to
provide lots of useful information for the OP, which you didn't.
[color=blue]
> Are you a yank ?[/color]

Well, that kind of thing obviously shows that rather you are the
'asshole' here. Or a dimwit. Pick what you prefer. Case closed.
--
\ Jens Thoms Toerring ___ Jens.Toerring@p hysik.fu-berlin.de
\______________ ____________ http://www.toerring.de

**Richard Bos** · Nov 14 '05, 03:44 PM

Re: Unix C programming for finding file

Mark McIntyre <markmcintyre@s pamcop.net> wrote:
[color=blue]
> On Thu, 25 Nov 2004 21:20:55 +0000, in comp.lang.c ,
> fallujahdestrot edbyusbastards@ peace.com wrote:
>[color=green]
> >Are you a yank ?[/color]
>
> Dan is swiss or german,[/color]

Rumanian, surely?

Richard

**Michael Mair** · Nov 14 '05, 03:44 PM

Re: Unix C programming for finding file

Richard Bos wrote:
[color=blue]
> Mark McIntyre <markmcintyre@s pamcop.net> wrote:
>
>[color=green]
>>On Thu, 25 Nov 2004 21:20:55 +0000, in comp.lang.c ,
>>fallujahdestr otedbyusbastard s@peace.com wrote:
>>
>>[color=darkred]
>>>Are you a yank ?[/color]
>>
>>Dan is swiss or german,[/color]
>
> Rumanian, surely?[/color]

Awgh, are you guys regulars? Do I know you?
Apart from the uselessness of this information: Have a
look at threads with Dan sniping at Joona I Palaste... ;-)

Cheers
Michael
--
E-Mail: Mine is an /at/ gmx /dot/ de address.

**Dan Pop** · Nov 14 '05, 03:45 PM

Re: Unix C programming for finding file

In <41a6de28.15177 5482@news.indiv idual.net> rlb@hoekstra-uitgeverij.nl (Richard Bos) writes:
[color=blue]
>Mark McIntyre <markmcintyre@s pamcop.net> wrote:
>[color=green]
>> On Thu, 25 Nov 2004 21:20:55 +0000, in comp.lang.c ,
>> fallujahdestrot edbyusbastards@ peace.com wrote:
>>[color=darkred]
>> >Are you a yank ?[/color]
>>
>> Dan is swiss or german,[/color]
>
>Rumanian, surely?[/color]

According to Mark's logic, I must be Swiss or German because I am known
to have a Swiss email address and a German email address. Now, where does
this Romanian nonsense come from? ;-)

Dan
--
Dan Pop
DESY Zeuthen, RZ group
Email: Dan.Pop@ifh.de
Currently looking for a job in the European Union

**Joe Wright** · Nov 14 '05, 03:45 PM

Re: Unix C programming for finding file

Richard Bos wrote:[color=blue]
> Mark McIntyre <markmcintyre@s pamcop.net> wrote:
>
>[color=green]
>>On Thu, 25 Nov 2004 21:20:55 +0000, in comp.lang.c ,
>>fallujahdestr otedbyusbastard s@peace.com wrote:
>>
>>[color=darkred]
>>>Are you a yank ?[/color]
>>
>>Dan is swiss or german,[/color]
>
>
> Rumanian, surely?
>
> Richard[/color]

Romanian.

Today's French and English texts refer to Romania while older German
seems to like Rumania. What's the difference?

How does Dan spell it?
--
Joe Wright mailto:joewwrig ht@comcast.net
"Everything should be made as simple as possible, but not simpler."
--- Albert Einstein ---

**Dan Pop** · Nov 14 '05, 03:45 PM

Re: Unix C programming for finding file

In <S8udnR9m1JORwT rcRVn-2Q@comcast.com> Joe Wright <joewwright@com cast.net> writes:
[color=blue]
>Richard Bos wrote:[color=green]
>>
>> Rumanian, surely?
>>
>> Richard[/color]
>
>Romanian.
>
>Today's French and English texts refer to Romania while older German
>seems to like Rumania. What's the difference?[/color]

"Rumania" and "Roumania" are a obsolete English spellings. "Romania"
is the current official English spelling. The French use "Roumanie"
and the Germans "Rumaenien" ("Rumänien" for people using Latin-1
fonts). The international abbreviation is RO, BTW.
[color=blue]
>How does Dan spell it?[/color]

When using a Latin-1 or Latin-2 font and writing in my native language:
"România".

Dan
--
Dan Pop
DESY Zeuthen, RZ group
Email: Dan.Pop@ifh.de
Currently looking for a job in the European Union

**Richard Tobin** · Nov 14 '05, 03:45 PM

Re: Unix C programming for finding file

In article <co7q5e$deo$2@s unnews.cern.ch> , Dan Pop <Dan.Pop@cern.c h> wrote:
[color=blue]
>"Rumania" and "Roumania" are a obsolete English spellings. "Romania"
>is the current official English spelling.[/color]

I wasn't aware that we had official spellings in English.

Do you mean it's the one that the Romanian government wants us to use?

-- Richard

**Craig Barkhouse** · Nov 14 '05, 03:45 PM

Re: Unix C programming for finding file

"Richard Tobin" <richard@cogsci .ed.ac.uk> wrote in message
news:co87e1$1mv n$2@pc-news.cogsci.ed. ac.uk...[color=blue]
> I wasn't aware that we had official spellings in English.[/color]

We do. In fact, there have been entire books -- called "dictionari es" -- on
the subject.

**Richard Tobin** · Nov 14 '05, 03:45 PM

Re: Unix C programming for finding file

In article <p0Opd.60663$Ro .2298486@news20 .bellglobal.com >,
Craig Barkhouse <cabarkho@stude nt.cs.uwaterloo .ca> wrote:
[color=blue][color=green]
>> I wasn't aware that we had official spellings in English.[/color][/color]
[color=blue]
>We do. In fact, there have been entire books -- called "dictionari es" -- on
>the subject.[/color]

How strange. I was not aware that they had an "official" status at all.

-- Richard

Unix C programming for finding file

Unix C programming for finding file

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