ofstream class -- error-checking

[pauldepstein]

How should I check that a stream (for example a .txt file or the screen
-- std::cout ) is open and ready to receive input.

To declare the stream as an instantiation of the ofstream class,
I write

ofstream mystream("filename");

// Then, to check the stream is ready, should I say

if (!mystream){ cerr << ...}

// or should I say

if (mystream.bad()) {cerr << ...}

What are the pros and cons of both methods (if they both work)?

Thank you very much for your help.


Paul Epstein

 

[Xiaobin.Huang]

if (!mystream){ cerr << ...}
this works well, means !mystream.good()
means the stream has broken already

stream has four status:
bool good() const; //the next operate should be success
bool eof() const; //end of file
bool fail() const; //the next operate should be failed
bool bad() const; //baddly, the stream has broken

the deffrence between fail() and bad() is, if one stream gets to fail()
but not in bad() status the same time, we can assume the stream can
work. If one stream gets to bad(), all are over.

The operator ! returns fail().

 

[pauldepstein]

this works well, means !mystream.good()

means the stream has broken already

stream has four status:
bool good() const; //the next operate should be success
bool eof() const; //end of file
bool fail() const; //the next operate should be failed
bool bad() const; //baddly, the stream has broken

the deffrence between fail() and bad() is, if one stream gets to fail()
but not in bad() status the same time, we can assume the stream can
work. If one stream gets to bad(), all are over.

The operator ! returns fail().

Very helpful!

Thank you,

Paul