Requirements:
Learn how to read and write text files
Learn how to read and write binary files C + + file stream:
FStream//File stream
Ifstream//input file stream
Ofstream//output file stream//create a text file and write information
Output information to a file as if it were output to the screen
#include
#include
void Main ()
{
Ofstream F1 ("D:\\me.txt"); Open the file for writing and create it if the file does not exist
if (!F1) return; Failure to open a file ends the run
f1< << "Name:" << "Cheap East" <
f1< << "Home Address:" << "Zhengzhou, Henan" <
F1.close (); Close File
}
After running, open the file D:\me.txt, which reads as follows:
Name: William Oriental
Home address: Zhengzhou, Henan
File operation:
Open File
Filename
Note that the slash in the path name is double-written, such as:
"D:\\myfiles\\readme.txt"
File Open With options:
Ios::in = 0x01,//read, File not present (ifstream default open mode)
Ios::out = 0x02,//write, the file does not exist, and if the file already exists, empty the original content (ofstream default open mode)
Ios::ate = 0x04,//When the file is opened, the pointer is at the end of the file. Can change the position of the pointer, often combined with in and out
Ios::app = 0x08,//write, the file does not exist, and if the file already exists, then writes the new content after the original file content, the pointer position is always at the last
Ios::trunc = 0x10,//Truncate the file length to 0 (default) before reading and writing
Ios::nocreate = 0x20,//The file does not exist and generates an error, often combined with in or app
Ios::noreplace = 0x40,//file generated error when present, common and out combined use
Ios::binary = 0x80//binary format file
File Protection options:
Filebuf::openprot; The default compatible sharing method
Filebuf::sh_none; Exclusive, not shared
Filebuf::sh_read; Read share
Filebuf::sh_write; Write sharing
Ways to open a file
Specify the file name and open mode when calling the constructor
Ifstream f ("D:\\12.txt", ios::nocreate); The default is to open the file as Ios::in, and the operation fails when the file does not exist
Ofstream f ("D:\\12.txt"); Open files by default in Ios::out mode
FStream f ("D:\\12.dat", ios::in|ios::out|ios::binary); Open a binary file as read-write
Using the Open member function
FStream F;
F.open ("D:\\12.txt", ios::out); Use the Open function when working with multiple files using the same object
Check if Open successfully
Success:
if (f) {...} The FStream object is not available for Ifstream, Ofstream objects.
if (F.good ()) {...}
Failed:
if (!f) {...} ! Operator is overloaded
if (F.fail ()) {...}
Read and write operations
Using the <<,>> operator
Only text files can be read and written, and used in binary files may produce errors.
Use function members get, put, read, write, and so on
The function that is often used in conjunction with Read is Gcount (), which is used to obtain the actual number of bytes read.
Read and write binary file considerations
Ios::binary must be specified in open mode, otherwise read-write error
Read and write with Read\write, but not with the insert, extract operator, or an error occurs.
Use the EOF () function to detect if a file is read-end, using Gcount () to get the actual number of bytes read
Close File
Use the member function close, such as:
F.close ();
Using destructors
The end of the object lifetime checks to see if the file is closed and closes the file without closing it.
Random Read and write files
You can read and write to a file at the specified location by moving the file read and write pointers.
SEEKG (absolute position); Absolute move,//input stream operation
SEEKG (relative position, reference position); Relative operation
Tellg (); Returns the current pointer position
SEEKP (absolute position); Absolute movement,//output stream operation
SEEKP (relative position, reference position); Relative operation
TELLP (); Returns the current pointer position
Reference location:
Ios::beg = 0//relative to file header
Ios::cur = 1//relative to the current position
Ios::end = 2//relative to end of file
Examples of reading and writing text files
To be able to correctly read the data written to the file, it is best to separate the data between
#include
void Main ()
{
FStream f ("D:\\try.txt", ios::out);
f<<1234<< ' <<3.14<< ' A ' << ' how is you '; Write Data
F.close ();
F.open ("D:\\try.txt", ios::in);
int i;
Double D;
char c;
Char s[20];
f>>i>>d>>c; Reading data
F.getline (s,20);
cout<
<
cout< <
cout< <
cout< <
F.close ();
}
Operation Result:
1234
3.14
A
How is You
Press any key to continue
Display the contents of a text file
Use Get () to read one character at a time--------------------------------scheme one
#include
void Main ()
{
Ifstream Fin ("d:\\ introduction. txt", ios::nocreate);
if (!fin) {
cout<< "File open error!\n";
Return
}
char c;
while ((C=fin.get ())!=eof) cout<
Fin.close ();
}
Use Get (char *,int n,char delim= ' \ n ') to read multiple characters at once----scenario two
Clever use of text files without the character ' \ S ' Feature for reading
#include
void Main ()
{
Ifstream Fin ("d:\\ introduction. txt", ios::nocreate);
if (!fin) {
cout<< "File open error!\n";
Return
}
Char c[80];
while (Fin.get (c,80, '!=null ') cout<
Fin.close ();
}
Using read (char *,int N) reading a file---------------------------scenario three
#include
void Main ()
{
Ifstream Fin ("d:\\ introduction. txt", ios::nocreate);
if (!fin) {
cout<< "File open error!\n";
Return
}
Char c[80];
while (!fin.eof ())//Determine if the file is read-end
{
Fin.read (c,80);
Cout.write (C,fin.gcount ());
}
Fin.close ();
}
Copy files
Binary File Operation example
#include
void Main ()
{
Ifstream fin ("C:\\1.exe", ios::nocreate|ios::binary);
if (!fin) {
cout<< "File open error!\n";
Return
}
Ofstream fout ("C:\\2.exe", ios::binary);
Char c[1024];
while (!fin.eof ())
{
Fin.read (c,1024);
Fout.write (C,fin.gcount ());
}
Fin.close ();
Fout.close ();
cout<< "Copy over!\n";
}
C + + file read and write open mode and so on compared all
