Why doesn't this code work?

[Rudolfs.Bundulis@gmail.com]

As I understood it's better to use fstream instead of fstream.h. When I
was porting my code (i'm using VC6.0++) i needed to let go of such
things as ios::noreplace and ios::nocreate. I neede to check if file
exists before creating it. If it exists we prompt that we are
overwriting. The files ar being passed in as command line arguments.

I did it like that:

#include <fstream>

std::fstream outFile;
....
....
....
outFile.open(ar gv[2],std::ios_base: :in);// the second argument is the
output file
if (! outFile)
{//file does not exist
outFile.open(ar gv[2],std::ios::out) ;
cout<<"Testing. ..";
}
else
{
cout<<"Warning: Output file already exists!\n";//prompt that it
exists
outFile.close() ;//close it
outFile.open(ar gv[2],std::ios::out) ; //open it for output
cout<<"Testing. ..";
}
outFile.close() ;

but this stuff didn't work if the file did not exist. It just created
an empty file;

I changed it like this:

std::ifstream tmpFile;
std::ofstream outFile;
....
....
tmpFile.open(ar gv[2],std::ios_base: :in);
if (!tmpFile)
{
outFile.open(ar gv[2],std::ios_base: :out);
cout<<"Testing. ..";

}
else
{
cout<<"Warning: Output file already exists!\n";
tmpFile.close() ;
outFile.open(ar gv[2],std::ios_base: :out);
cout<<"Testing. ..";
}
outFile.close() ;

this stuff works fine, but i would like to get rid of the tmpFile (if
possible).
Any ideas? Why didn' t the first one work?

[Victor Bazarov]

Re: Why doesn't this code work?

Rudolfs.Bunduli s@gmail.com wrote:

As I understood it's better to use fstream instead of fstream.h. When
I was porting my code (i'm using VC6.0++) i needed to let go of such
things as ios::noreplace and ios::nocreate. I neede to check if file
exists before creating it. If it exists we prompt that we are
overwriting. The files ar being passed in as command line arguments.
>
I did it like that:
>
#include <fstream>
>
std::fstream outFile;
...
...
...
outFile.open(ar gv[2],std::ios_base: :in);// the second argument is the
output file
if (! outFile)
{//file does not exist
outFile.open(ar gv[2],std::ios::out) ;
cout<<"Testing. ..";
}
else
{
cout<<"Warning: Output file already exists!\n";//prompt that it
exists
outFile.close() ;//close it
outFile.open(ar gv[2],std::ios::out) ; //open it for output
cout<<"Testing. ..";
}
outFile.close() ;
>
but this stuff didn't work if the file did not exist. It just created
an empty file;
>
I changed it like this:
>
std::ifstream tmpFile;
std::ofstream outFile;
...
...
tmpFile.open(ar gv[2],std::ios_base: :in);
if (!tmpFile)
{
outFile.open(ar gv[2],std::ios_base: :out);
cout<<"Testing. ..";
>
}
else
{
cout<<"Warning: Output file already exists!\n";
tmpFile.close() ;
outFile.open(ar gv[2],std::ios_base: :out);
cout<<"Testing. ..";
}
outFile.close() ;
>
this stuff works fine, but i would like to get rid of the tmpFile (if
possible).
Any ideas? Why didn' t the first one work?

First off, you're using a rather old compiler/library implemenation.
Perhaps you should consider switching to a more up-to-date release
of their compiler/library.

Second, if the behaviour is specific to VC++, you need to ask in the
VC++ newsgroup (microsoft.publ ic.vc.language) .

Third, when handling files (existence, etc.) it is recommended to use
platform-specific mechanisms. I am sure you can always request the
OS to give you the status of the file. Standard means (as you are
finding out) are not very generic in those areas.

V
--
Please remove capital 'A's when replying by e-mail
I do not respond to top-posted replies, please don't ask

[BobR]

Re: Why doesn't this code work?


Victor Bazarov wrote in message ...

>Rudolfs.Bundul is@gmail.com wrote:

>As I understood it's better to use fstream instead of fstream.h. When
>I was porting my code (i'm using VC6.0++) i needed to let go of such
>things as ios::noreplace and ios::nocreate. I neede to check if file
>exists before creating it. If it exists we prompt that we are
>overwriting. The files ar being passed in as command line arguments.
>I did it like that:
>>
>#include <fstream>
>...
>I changed it like this:
>>
>std::ifstrea m tmpFile;
>std::ofstrea m outFile;
>...
>tmpFile.open(a rgv[2],std::ios_base: :in);
>if (!tmpFile){
>outFile.open(a rgv[2],std::ios_base: :out);
> cout<<"Testing. ..";
>}
>else{
>cout<<"Warning : Output file already exists!\n";
>tmpFile.close( );
>outFile.open(a rgv[2],std::ios_base: :out);
> cout<<"Testing. ..";
>}
>outFile.close( );
>>
>this stuff works fine, but i would like to get rid of the tmpFile (if
>possible).
>Any ideas? Why didn' t the first one work?

>
>
>Third, when handling files (existence, etc.) it is recommended to use
>platform-specific mechanisms.

Ouch!

[ from an old post ]
// nwadc10 wrote:
// I'm having trouble checking to see if a file already exists.
// Use the stat method which is portable on Windows, UNIX, Linux, and most
OS.

// other includes here
#include <sys/stat.h // hmmm, maybe not as portable??

bool FileExist(char const *FileName){
struct stat my_stat;
return (stat(FileName, &my_stat) == 0);
}

bool IsDirectory(cha r const *FileName){
struct stat my_stat;
if(stat(FileNam e, &my_stat) != 0) return false;
return ((my_stat.st_mo de & S_IFDIR) != 0);
}

// Many times, it's not just important to determind if the file exist, but
// it's also important to determind if it a file or directory.
// ----------------------------------------------------------------------


// int main(int argc, char* argv[]){
void FileExistMain(s td::ostream &cout = std::cout){
// using std::cout // for NG posting
bool v1 = FileExist("c:/autoexec.bat");
bool v2 = FileExist("c:/nofile.bat");
bool v3 = FileExist("c:/config.sys");
bool v4 = FileExist("c:/nofile2.bat");
bool v5 = IsDirectory("c:/windows");
bool v6 = IsDirectory("c:/notA_dir");
bool v7 = IsDirectory("c:/WINNT");

cout<<"bool v1 = FileExist(\"c:\ \autoexec.bat\" ); ="<<v1<<std::en dl;
cout<<"bool v2 = FileExist(\"c:\ \nofile.bat\"); ="<<v2<<std::en dl;
cout<<"bool v3 = FileExist(\"c:\ \config.sys\"); ="<<v3<<std::en dl;
cout<<"bool v4 = FileExist(\"c:\ \nofile2.bat\") ; ="<<v4<<std::en dl;
cout<<"bool v5 = IsDirectory(\"c :\\windows\"); ="<<v5<<std::en dl;
cout<<"bool v6 = IsDirectory(\"c :\\notA_dir\"); ="<<v6<<std::en dl;
cout<<"bool v7 = IsDirectory(\"c :\\WINNT\"); ="<<v7<<std::en dl;
return;
}

I did not save the posters name, so, I can not credit him/her.

--
Bob R
POVrookie

[Marcus Kwok]

Re: Why doesn't this code work?

BobR <RemoveBadBobR@ worldnet.att.ne twrote:

[ from an old post ]
// nwadc10 wrote:
// I'm having trouble checking to see if a file already exists.
// Use the stat method which is portable on Windows, UNIX, Linux, and most
OS.
>
// other includes here
#include <sys/stat.h // hmmm, maybe not as portable??
>
bool FileExist(char const *FileName){
struct stat my_stat;
return (stat(FileName, &my_stat) == 0);
}
>
bool IsDirectory(cha r const *FileName){
struct stat my_stat;
if(stat(FileNam e, &my_stat) != 0) return false;
return ((my_stat.st_mo de & S_IFDIR) != 0);
}
>
// Many times, it's not just important to determind if the file exist, but
// it's also important to determind if it a file or directory.
// ----------------------------------------------------------------------
>
I did not save the posters name, so, I can not credit him/her.

http://www.codecomments.com/archive3...10-664071.html
seems to say that it was Axter.

--
Marcus Kwok
Replace 'invalid' with 'net' to reply

[BobR]

Re: Why doesn't this code work?


Marcus Kwok wrote in message ...

>BobR wrote:

>>
>I did not save the posters name, so, I can not credit him/her.

>
>http://www.codecomments.com/archive3...10-664071.html
>seems to say that it was Axter.

Thank you, Marcus.
[ I made note of that in my header file for future ref.. ]

I have a slow connection and limited hours due to budget (un-employed). I
appreciate your time & effort.

Any comment on the portability of this header?
#include <sys/stat.h // hmmm, maybe not as portable??

--
Bob R
POVrookie

[Larry Smith]

Re: Why doesn't this code work?

BobR wrote:

Marcus Kwok wrote in message ...

>BobR wrote:

>>I did not save the posters name, so, I can not credit him/her.

>http://www.codecomments.com/archive3...10-664071.html
>seems to say that it was Axter.

>
Thank you, Marcus.
[ I made note of that in my header file for future ref.. ]
>
I have a slow connection and limited hours due to budget (un-employed). I
appreciate your time & effort.
>
Any comment on the portability of this header?
#include <sys/stat.h // hmmm, maybe not as portable??
>
--
Bob R
POVrookie
>
>

It's portable to most Unix/Linux versions.

[Marcus Kwok]

Re: Why doesn't this code work?

BobR <RemoveBadBobR@ worldnet.att.ne twrote:

>
Marcus Kwok wrote in message ...

>>BobR wrote:

>>>
>>I did not save the posters name, so, I can not credit him/her.

>>
>>http://www.codecomments.com/archive3...10-664071.html
>>seems to say that it was Axter.

>
Thank you, Marcus.
[ I made note of that in my header file for future ref.. ]
>
I have a slow connection and limited hours due to budget (un-employed). I
appreciate your time & effort.

It wasn't much effort really... since in the original post "determind"
is misspelled :)

Any comment on the portability of this header?
#include <sys/stat.h // hmmm, maybe not as portable??

AFAIK anything in sys/ is not a standard header in terms of C++, but
maybe it is considered a standard POSIX header.

--
Marcus Kwok
Replace 'invalid' with 'net' to reply