fopen help.

chriscolden · 01-10-2006, 03:36 PM

Hi,

I am having a problem with fopen. I have searched the forum but with no luck.

i am trying to open a binary file using fopen. I am using Borland C++ 3.1 and it cannot open the file. fopen gives a NULL pointer. When opening the same program in Turbo C++ for Windows it seems to work correctly.

the file is stored in the follow location

J:\dsaaIII\ass1\Program 3\DATABASE.BIN

This is my code

Code:

char fname[]="J:\\dsaaIII\\ass1\\Program 3\\DATABASE.BIN";

FILE * ptrFile;

ptrFile=fopen(fname, "rt");

if(ptrFile==NULL){
         printf("\n Error Opening Database File!\n\n Please Press Any Key To Continue >");
         getch();

         clrscr();

         return 0;
}

fread( lastRecordID, sizeof(int), 1, ptrFile );

fclose(ptrFile);

The above is a code snippet. The actual fuction is more complex. however it should still be able to open the file. which it is clearly failing.

Thanks in advance.

Chris

PING · 01-10-2006, 03:59 PM

You probably want to open the file in binary mode. Use "rb" instead of "rt" as your second parameter to fopen()

swoopy · 01-10-2006, 04:00 PM

>J:\\dsaaIII\\ass1\\Program 3\\DATABASE.BIN
Borland C++ 3.1 probably doesn't support directories/filenames longer than eight characters. Under DOS, "Program 3" would probably equate to a name like "Progra~1".

dwks · 01-10-2006, 04:00 PM

Turbo C++ might only support 8.3 filenames. Or else you might need quotes:

Code:

char fname[]="\"J:\\dsaaIII\\ass1\\Program 3\\DATABASE.BIN\"";

If you support only 8.3 filenames, find out the DOS name for "Program 3".

dwks · 01-10-2006, 04:02 PM

Quote:

Under DOS, "Program 3" would probably equate to a name like "Program~1".

Under Windows-based DOS, you mean, like Windows 98. Windows XP will give it a random 8.3 name. To find out what it is, type this from a command prompt:

Code:

C>J:

C>cd \dsaaIII\ass1\

C>dir "Program 3"

swoopy · 01-10-2006, 04:21 PM

>Windows XP will give it a random 8.3 name.
Are you sure? Because under the Windows XP version I'm using it doesn't appear to be random.

chriscolden · 01-10-2006, 04:21 PM

Hey, thanks for your help so far.

I got...

Directory of J:\dsaaIII\ass\Program 3

.... does this mean its ok??

Chris

dwks · 01-10-2006, 04:24 PM

Oops, my mistake. Use

Code:

C>dir program*

instead, and it might print something like

Code:

qwerty <DIR> 11-11-11 12.00p Program 3

The "qwerty" part is the part you want. See what it is.

dwks · 01-10-2006, 04:26 PM

Quote:

>Windows XP will give it a random 8.3 name.
Are you sure? Because under the Windows XP version I'm using it doesn't appear to be random.

Windows 2k/2k3/xp Long Filename Truncation

Quote:

*edit*DWKS: if you try what he says, you see that the file names don't end up looking like that, copy of text document.txt, turns into co0dfb~1.txt for example.

I thought it would be like that, too, but it seems random to me.

chriscolden · 01-10-2006, 04:29 PM

i have just tried that but cannot seem to make it display anythin random.

Chris

dwks · 01-10-2006, 04:33 PM

Can you post the output of the dir command?

Unless the double-quote thing solved the problem, in which case don't bother.

chriscolden · 01-10-2006, 04:38 PM

Thanks for all your help.

I have got it working now.

It was because i was typing the wrong thing into dos. I have got the shorter name for the folder Program 3 and it seems to work ok now.

Thanks again

Chris

swoopy · 01-10-2006, 05:17 PM

>I thought it would be like that, too, but it seems random to me.
Well I wasn't using the dir command, but instead was using a 16-bit windows program, and it wasn't coming up random. Tomorrow I'll try the dir command and see what it displays.

swoopy · 01-11-2006, 07:28 AM

Ok, I tried the dir command on my XP machine, and the 8.3 filenames are not random. Maybe someone else can try it on XP and see what they get.

dwks · 01-11-2006, 01:20 PM

I would expect it to be non-random. But my link seems to suggest otherwise.

01-10-2006, 03:36 PM	#1
chriscolden Registered User Join Date: Jan 2006 Posts: 32	fopen help. Hi, I am having a problem with fopen. I have searched the forum but with no luck. i am trying to open a binary file using fopen. I am using Borland C++ 3.1 and it cannot open the file. fopen gives a NULL pointer. When opening the same program in Turbo C++ for Windows it seems to work correctly. the file is stored in the follow location J:\dsaaIII\ass1\Program 3\DATABASE.BIN This is my code Code: char fname[]="J:\\dsaaIII\\ass1\\Program 3\\DATABASE.BIN"; FILE * ptrFile; ptrFile=fopen(fname, "rt"); if(ptrFile==NULL){ printf("\n Error Opening Database File!\n\n Please Press Any Key To Continue >"); getch(); clrscr(); return 0; } fread( lastRecordID, sizeof(int), 1, ptrFile ); fclose(ptrFile); The above is a code snippet. The actual fuction is more complex. however it should still be able to open the file. which it is clearly failing. Thanks in advance. Chris
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01-10-2006, 03:59 PM	#2
PING Registered User Join Date: Nov 2004 Location: india Posts: 493	You probably want to open the file in binary mode. Use "rb" instead of "rt" as your second parameter to fopen() __________________ Go Petr !! My Blog
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01-10-2006, 04:00 PM	#3
swoopy Registered User Join Date: Oct 2001 Posts: 2,936	>J:\\dsaaIII\\ass1\\Program 3\\DATABASE.BIN Borland C++ 3.1 probably doesn't support directories/filenames longer than eight characters. Under DOS, "Program 3" would probably equate to a name like "Progra~1". __________________ http://www.freechess.org
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01-10-2006, 04:00 PM	#4
dwks Frequently Quite Prolix Join Date: Apr 2005 Location: Canada Posts: 7,698	Turbo C++ might only support 8.3 filenames. Or else you might need quotes: Code: char fname[]="\"J:\\dsaaIII\\ass1\\Program 3\\DATABASE.BIN\""; If you support only 8.3 filenames, find out the DOS name for "Program 3". __________________ dwk Seek and ye shall find. quaere et invenies. "Simplicity does not precede complexity, but follows it." -- Alan Perlis "Testing can only prove the presence of bugs, not their absence." -- Edsger Dijkstra "The only real mistake is the one from which we learn nothing." -- John Powell Other boards: DaniWeb, TPS Unofficial Wiki FAQ: cpwiki.sf.net My website: http://dwks.theprogrammingsite.com/ Projects: codeform, xuni, atlantis, nort, etc.
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01-10-2006, 04:21 PM	#6
swoopy Registered User Join Date: Oct 2001 Posts: 2,936	>Windows XP will give it a random 8.3 name. Are you sure? Because under the Windows XP version I'm using it doesn't appear to be random. __________________ http://www.freechess.org
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01-10-2006, 04:24 PM	#8
dwks Frequently Quite Prolix Join Date: Apr 2005 Location: Canada Posts: 7,698	Oops, my mistake. Use Code: C>dir program* instead, and it might print something like Code: qwerty <DIR> 11-11-11 12.00p Program 3 The "qwerty" part is the part you want. See what it is. __________________ dwk Seek and ye shall find. quaere et invenies. "Simplicity does not precede complexity, but follows it." -- Alan Perlis "Testing can only prove the presence of bugs, not their absence." -- Edsger Dijkstra "The only real mistake is the one from which we learn nothing." -- John Powell Other boards: DaniWeb, TPS Unofficial Wiki FAQ: cpwiki.sf.net My website: http://dwks.theprogrammingsite.com/ Projects: codeform, xuni, atlantis, nort, etc.
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01-10-2006, 04:29 PM	#10
chriscolden Registered User Join Date: Jan 2006 Posts: 32	i have just tried that but cannot seem to make it display anythin random. Chris
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01-10-2006, 04:33 PM	#11
dwks Frequently Quite Prolix Join Date: Apr 2005 Location: Canada Posts: 7,698	Can you post the output of the dir command? Unless the double-quote thing solved the problem, in which case don't bother. __________________ dwk Seek and ye shall find. quaere et invenies. "Simplicity does not precede complexity, but follows it." -- Alan Perlis "Testing can only prove the presence of bugs, not their absence." -- Edsger Dijkstra "The only real mistake is the one from which we learn nothing." -- John Powell Other boards: DaniWeb, TPS Unofficial Wiki FAQ: cpwiki.sf.net My website: http://dwks.theprogrammingsite.com/ Projects: codeform, xuni, atlantis, nort, etc.
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01-10-2006, 04:38 PM	#12
chriscolden Registered User Join Date: Jan 2006 Posts: 32	Thanks for all your help. I have got it working now. It was because i was typing the wrong thing into dos. I have got the shorter name for the folder Program 3 and it seems to work ok now. Thanks again Chris
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01-10-2006, 05:17 PM	#13
swoopy Registered User Join Date: Oct 2001 Posts: 2,936	>I thought it would be like that, too, but it seems random to me. Well I wasn't using the dir command, but instead was using a 16-bit windows program, and it wasn't coming up random. Tomorrow I'll try the dir command and see what it displays. __________________ http://www.freechess.org
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01-11-2006, 07:28 AM	#14
swoopy Registered User Join Date: Oct 2001 Posts: 2,936	Ok, I tried the dir command on my XP machine, and the 8.3 filenames are not random. Maybe someone else can try it on XP and see what they get. __________________ http://www.freechess.org
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01-11-2006, 01:20 PM	#15
dwks Frequently Quite Prolix Join Date: Apr 2005 Location: Canada Posts: 7,698	I would expect it to be non-random. But my link seems to suggest otherwise. __________________ dwk Seek and ye shall find. quaere et invenies. "Simplicity does not precede complexity, but follows it." -- Alan Perlis "Testing can only prove the presence of bugs, not their absence." -- Edsger Dijkstra "The only real mistake is the one from which we learn nothing." -- John Powell Other boards: DaniWeb, TPS Unofficial Wiki FAQ: cpwiki.sf.net My website: http://dwks.theprogrammingsite.com/ Projects: codeform, xuni, atlantis, nort, etc.
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