How can I get a file descriptor from a c++ i/o stream?

[Thorsten Knopel]

Dear all,

Because of some reason, I must get a file descript from a c++ I/O stream,
for example: ifstream.

Under OpenUnix I have a function ifstream::fd (rdbuf->fd) to do this.
But in Linux, there is not a such function of ifstream class.
Is there not a such function in standard C++ ?
Or is there another way to get?

Thanks for your help.
Regards,
Thorsten

 

[Victor Bazarov]

Because of some reason, I must get a file descript from a c++ I/O stream,
for example: ifstream.

Under OpenUnix I have a function ifstream::fd (rdbuf->fd) to do this.
But in Linux, there is not a such function of ifstream class.
Is there not a such function in standard C++ ?

No. In general a stream doesn't have to have anything like a "file
descriptor" in it. It's implementation-defined how streams maintain
their association with whatever is considered "a file".

Or is there another way to get?

There can be something specific to your library implementation. Have
you tried looking in the docs or asking in a newsgroup for your OS?

V

 

[Pete Becker]

It's implementation-defined how streams maintain
their association with whatever is considered "a file".

It's unspecified, not implementation defined. The implementation doesn't
have to document what it does.