IO Standard library types and header files

iostream istream Read from stream
ostream Write in the stream
iostream Read and write to the stream ; from istream and ostream Derived from
fstream ifstream Read from file ; from istream Derived from
ofstream Write it in the file ; from ostream Derived from
fstream Read and write files ; from iostream Derived from
sstream istringstream from string Object ; from istream Derived from
ostringstream writes string Go to the object ; from ostream Derived from
stringstream Yes string Object to read and write ; from iostream Derived from

1 When a file stream object is used again, it is necessary to first clear

ifstream& open_file(ifstream &in, const string &file)
{
in.close(); // close in case it was already open
in.clear(); // clear any existing errors
// if the open fails, the stream will be in an invalid state
in.open(file.c_str()); // open the file we were given
return in; // condition state is good if open succeeded
}

2 Check object status when opening a file

ifstream input;
vector<string>::const_iterator it = files.begin();
// for each file in the vector
while (it != files.end()) {
input.open(it->c_str()); // open the file
// if the file is ok, read and "process" the input
if (!input)
break; // error: bail out!
while(input >> s) // do the work on this file
process(s);
input.close(); // close file when we're done with it
input.clear(); // reset state to ok
++it; // increment iterator to get next file
}

3 File open mode combination

out Open the file for writing , Delete the existing data in the file
out | app Open the file for writing , Write... At the end of the file
out | trunc And out Same pattern
in Open the file for reading
in | out Open the file to read 、 Write operations , And set it at the beginning of the file
in | out | trunc Open the file to read 、 Write operations , Delete the existing data in the file

C++Primer,C++ standard IO Library to read more about the experience of the article

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