operating on files in C++ need help

[Rex_chaos]

I am a c programmer and new to C++. In C, I am familiar with some
operations on file. Now when shifting from c to c++, using iostream, I
have no idea how to perform the following operations

1. check if a file or directory exists or not
2. delete all the files under a given directory
3. rename

[WW]

Rex_chaos wrote:

I am a c programmer and new to C++. In C, I am familiar with some
operations on file. Now when shifting from c to c++, using iostream, I
have no idea how to perform the following operations

1. check if a file or directory exists or not
Directory: no standard way to do it. Neither in C nor in C++. POSIX
provides something and Boost has a fairly portable library.

Files: again, there is no portable way AFAIK. You can try to open it. If
you can, it is there. If you cannot, it might not be there or you have no
rights or...
2. delete all the files under a given directory
No portable way. Again POSIX or Boost can help:
http://www.boost.org/libs/filesystem/doc/index.htm
3. rename

std::rename, as in C.

--
WW aka Attila

[Jonathan Mcdougall]

> I am a c programmer and new to C++. In C, I am familiar with some

operations on file. Now when shifting from c to c++, using iostream, I
have no idea how to perform the following operations

1. check if a file or directory exists or not
std::ifstream check("file.ext ");

if ( ! check )
std::cout << "file does not exist";
2. delete all the files under a given directory
No, unless you have the file list. Remove a single file with

std::remove("fi lename");

from <cstdio> iirc. You'll have to use some implementation-specific
functions to get more informations about the file system.
3. rename

No, except by copying under a new name and then remove the old
one.
Jonathan

[WW]

Jonathan Mcdougall wrote:

I am a c programmer and new to C++. In C, I am familiar with some
operations on file. Now when shifting from c to c++, using iostream,
I have no idea how to perform the following operations

1. check if a file or directory exists or not

std::ifstream check("file.ext ");

if ( ! check )
std::cout << "file does not exist";

Which can fail for a thousand other reasons. No rights, temporary network
problem, file is opened exclusively by someone else etc. etc. etc.

3. rename

No, except by copying under a new name and then remove the old
one.

How about the std::rename function in cstdio.h?

--
WW aka Attila

[Rob Williscroft]

Jonathan Mcdougall wrote in news:Y0Efb.5836 2$1M6.1109254
@wagner.videotr on.net:

I am a c programmer and new to C++. In C, I am familiar with some
operations on file. Now when shifting from c to c++, using iostream, I
have no idea how to perform the following operations

1. check if a file or directory exists or not
std::ifstream check("file.ext ");

if ( ! check )
std::cout << "file does not exist";

All this realy tells you is there was an error when you tried
to open the file for reading, It may be enough to know this but
it isn't a portable "file does not exist".

You could, having failed to open it, then try to create and write
to it, if this succeeds then the file *probably* didn't exist.

2. delete all the files under a given directory

No, unless you have the file list. Remove a single file with

std::remove("fi lename");

from <cstdio> iirc. You'll have to use some implementation-specific
functions to get more informations about the file system.

3. rename

No, except by copying under a new name and then remove the old
one.

int std::rename(con st char *old, const char *new);

http://www.dinkumware.com/manuals/re...io.html#rename
Rob.
--
http://www.victim-prime.dsl.pipex.com/

[Kevin Goodsell]

WW wrote:

How about the std::rename function in cstdio.h?

<cstdio>, no '.h'.

-Kevin
--
My email address is valid, but changes periodically.
To contact me please use the address from a recent posting.

[WW]

Kevin Goodsell wrote:

WW wrote:

How about the std::rename function in cstdio.h?

<cstdio>, no '.h'.

Well said. :-)

--
WW aka Attila

[Jonathan Mcdougall]

> >> 3. rename

No, except by copying under a new name and then remove the old
one.

How about the std::rename function in cstdio.h?

That`s the second time I forget it. Sorry.
Jonathan

[Mike Wahler]

"Rex_chaos" <re*******@21cn .com> wrote in message
news:f7******** *************** **@posting.goog le.com...

I am a c programmer and new to C++. In C, I am familiar with some
operations on file. Now when shifting from c to c++, using iostream, I
have no idea how to perform the following operations

1. check if a file or directory exists or not
Neither C nor C++ has the capability for this.
2. delete all the files under a given directory
Neither C nor C++ has the capability for this.
3. rename

Both C and C++ have a standard function for this.
Interestingly, its name is 'rename'. (Declared
by standard header <stdio.h> in C, <stdio.h>
or <cstdio> in C++.

-Mike

[Mike Wahler]

"Jonathan Mcdougall" <jo************ ***@DELyahoo.ca > wrote in message
news:Y0******** *************@w agner.videotron .net...

I am a c programmer and new to C++. In C, I am familiar with some
operations on file. Now when shifting from c to c++, using iostream, I
have no idea how to perform the following operations

1. check if a file or directory exists or not
std::ifstream check("file.ext ");

if ( ! check )
std::cout << "file does not exist";

That is an invalid conclusion. The only valid conclusion
is "Cannot open the file".

2. delete all the files under a given directory
No, unless you have the file list. Remove a single file with

std::remove("fi lename");

from <cstdio> iirc. You'll have to use some implementation-specific
functions to get more informations about the file system.

3. rename

No,

Yes.
except by copying under a new name and then remove the old
one.

See standard function 'rename()'

-Mike