C ++ primer Study Notes (chapter 8 standard Io Library)

Chapter 8 StandardsIoLibrary

Istream,Ostream,CIN,Cout,Cerr,>,<,

GetlineFunction.IstreamAndStringTwo reference parameters of the type.

8.1Object-oriented standard library

IoStandard library type and header file

Iostream

Fstream

Sstream

IoObjects cannot be copied or assigned values.

8.2Condition status

1. IoCondition status inside the Standard Library:

2. STRM: iostateByIostreamClass Definition, used to define the condition status

STRM: badbit STRM: iostateIndicates the destroyed stream.

STRM: failbit STRM: iostateIndicates the failed stream.

STRM: eofbit STRM: iostateType value, used to indicate that the stream has reached the end of the file

2,IoStandard Library condition status acquisition and modification functions

S. EOF ()If a stream is setSOfEofbitValue. This function returnsTrue

S. Bad ()If a stream is setSOfBadbitValue. This function returnsTrue

S. Fail ()If a stream is setSOfFailbitValue. This function returnsTrue

S. Good ()If the streamSThe function returnsTrue

S. Clear ()Clear streamSAnd setTrue

S. Clear (FLAG)StreamSIs setTrue.Flag, Type isSTRM: iostate

S. setstate (FLAG)StreamS.Flag, Type isSTRM: iostate

S. rdstate ()Get streamSThe current condition. The return value type isSTRM: iostateif (CIN )//Directly check the stream status

If (CIN )//Directly check the stream status

While (CIN> word )//Detects the stream returned by the expression and indirectly checks the stream status.

Int ival;

Whle (CIN> ival ,! Cin. EOF ()){

If (CIN. Bad ())

Throw runtime_error ("Io stream upted ");

If (cinj. Fail ()){

Cerr <"Bad Data, try again .";

Cin. Clear (istream: goodbit );

Cin. Ignore (STD: numeric_limits <STD: streamsize >:: max (), '\ n ');

Continue;

}

}

//ThisProgramRead continuouslyCIN, Until the end of the file or an unrecoverable read error occurs.

8.3Manage the output buffer

1.Refresh the output buffer

Cout <"Hi! "<Ends ;//Refresh the buffer without adding any data

Cout <"Hi! "<Endl ;//Refresh the buffer and add a line break

Cout <"Hi! "<Flush ;//Refresh the buffer and add any dataNull.

2. unitbufOperator

Cout <unitbuf <"first" <"second" <nounitbuf;

Equivalent

Cout <"first" <flush <"second" <flush;

NounitbufThe operator restores the stream to normal, and is refreshed by the System-managed buffer.

Worning: If the program crashes, the buffer will not be refreshed.

 

8.4File Input and Output

IfstreamRead files

OfstreamWrite files

FstreamRead and write the same file

The following program creates a fileD.txtAnd read to the screen.

 
# Include <iostream> # include <fstream> # include <string> using namespace STD; int main () {string STR; ofstream out ("d.txt "); STR = "ABCD \ nefgh \ nabcd \ ndfgh \ n"; out <STR <Endl; ifstream in ("d.txt"); For (string STR; Getline (in, str);) cout <STR <"\ n"; return 0 ;}
 

Copy the fileD.txtCopyA.txt

# Include <iostream> # include <fstream> # include <string> using namespace STD; int main () {string STR; ifstream in ("d.txt "); ofstream out ("a.txt"); For (string STR; Getline (in, STR);) out <STR <"\ n "; cout <"file copied successfully"; return 0 ;}