dev-cpp-users

RE: [Dev-C++] File Existence

[<Mat...@Ve...>]

Also when you open a stream, checking it like a boolean will fail if the
file open failed:

For example:

#include <ifstream>
#include <stdexcept>
...
    ifstream foo;
    if(!foo) throw runtime_error("Could not open file.");

-----Original Message-----
From: dev...@li...
[mailto:dev...@li...]On Behalf Of Farzan
Hajian
Sent: Friday, May 20, 2005 2:31 AM
To: dev...@li...
Subject: [Dev-C++] File Existence


Hi,
I'v written a small program which simulates the DOS command "type". The  
program receives
a file name form the command line. I used "fail()" function to check  
existence of the received
file. I have not used "ifstream" functions a lot and I want to know  
whether this is the
proper way to do so or not.
There is another function called "bad()". Please tell me what kind of  
errors it can detect.
I tried it in my program and it couldn't check existence of files.

#include <iostream>
#include <fstream>
#include <cstdlib>

using namespace std;

int main(int argc,char* arg[])
{
     if(argc==2)
     {
         ifstream File(arg[1]);
         char ch;
         if(File.fail())
             cout << "File not found!\n";
         else
             while(true)
             {
                 File.get(ch);
		if(File.eof())
		     break;
                 cout << ch;
             }
     }
     system("pause>null");
}

Thanks.


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RE: [Dev-C++] File Existence

[<A_B...@gm...>]

Well, it's a little bit unconventional, but I check file existans in this way:

if(FILE* f  = fopen("file", "r")){
  fclose(f);
  // file exists
  ...
}else{
  // file doesn't exist
  ...
}

What speaks against this method ???

CU, Acki

RE: [Dev-C++] File Existence

[Per W. <pw...@ia...>]

Have you looked at the access() function - specifically there to check for
existence - or specific rights - for a file.

/Per W

On Fri, 20 May 2005 A_B...@gm... wrote:

> Well, it's a little bit unconventional, but I check file existans in this way:
>
> if(FILE* f  = fopen("file", "r")){
>   fclose(f);
>   // file exists
>   ...
> }else{
>   // file doesn't exist
>   ...
> }
>
> What speaks against this method ???
>
> CU, Acki

RE: [Dev-C++] File Existence

[Gilles C. <cre...@ya...>]

Hello,

with function "fstat" , you have possibility to
receive size of file , owner ,.... and existence (+
portability).


Gilles

--- Per Westermark <pw...@ia...> a écrit:
> Have you looked at the access() function -
> specifically there to check for
> existence - or specific rights - for a file.
> 
> /Per W
> 
> On Fri, 20 May 2005 A_B...@gm... wrote:
> 
> > Well, it's a little bit unconventional, but I
> check file existans in this way:
> >
> > if(FILE* f  = fopen("file", "r")){
> >   fclose(f);
> >   // file exists
> >   ...
> > }else{
> >   // file doesn't exist
> >   ...
> > }
> >
> > What speaks against this method ???
> >
> > CU, Acki
> 
> 
> 
>
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RE: [Dev-C++] File Existence

[Per W. <pw...@ia...>]

You mean the portability that have made M$ rename that function to
_fstat() - at the same time they renamed _mkdir(), _open(), _close(),
_read(), _write(), _chmod(), _access(), _chdir(), ...

For just quick-checking existence or read or write access, access() is the
nicest function - no structs and extra tests needed.

stat(), fstat(), lstat() are more powerful, but requires more work - extra
include files and a struct stat variable.

On the other hand. If the intention is to actually open and/or create the
file, there is normally no need to pre-check existence. The used open
command can handle it.

/Per W

On Fri, 20 May 2005, Gilles Crebassa wrote:

> Hello,
>
> with function "fstat" , you have possibility to
> receive size of file , owner ,.... and existence (+
> portability).
>
>
> Gilles
>
> --- Per Westermark <pw...@ia...> a =E9crit:
> > Have you looked at the access() function -
> > specifically there to check for
> > existence - or specific rights - for a file.
> >
> > /Per W
> >
> > On Fri, 20 May 2005 A_B...@gm... wrote:
> >
> > > Well, it's a little bit unconventional, but I
> > check file existans in this way:
> > >
> > > if(FILE* f  =3D fopen("file", "r")){
> > >   fclose(f);
> > >   // file exists
> > >   ...
> > > }else{
> > >   // file doesn't exist
> > >   ...
> > > }
> > >
> > > What speaks against this method ???
> > >
> > > CU, Acki