Ah, copying a file — something so simple, it happens all the time. Copy this file there; copy that file here. But what exactly takes place when you copy a file? You actually create a new file, and fill it with the same contents as the original file. And how do you do that?
Well, it sounds like you have to read each and every byte from the first file, and write it to the second. Big-time yuck.
In fact, C has a general mechanism for reading and writing files, which is more flexible than redirection alone. Iostream.h and fstream.h There are types and functions in the library iostream.h that are used for standard I/O. Fstream.h includes the definitions for stream classes ifstream (for input from a file), ofstream (for output to a file. Jan 22, 2014 This c Video tutorial introduces you to file handling and explains how to create and open files. You are gonna learn how to use classes such as fstream, ifstream, ofstream, how to create.
But to make matters worse, copying a file means you have to make sure that you copy it exactly the same, that you don’t accidentally tack an extra 0 or two at the end of the file, or an extra carriage return or linefeed at the end of the file (which could happen when you copy a text file).
When all is done, the two files should be identical — not only contain the same information, but also be the same size.
And on top of all that, most good copy routines do even more! They give the new file a date that matches the date of the original file, and they will set all the attributes — including, say, read-only if the original is a read-only file. (If the file is read-only, then maybe you shouldn’t be able to copy it in the first place. . .)
Suddenly copying a file doesn’t sound so easy after all!
If you’re programming in Windows, you’re in luck! As long as you’re not using the ancient Windows 3.1, you get a CopyFile function! To get ready to use it, you include the line #include <windows.h> in your application. Then here’s all you have to do:
This copies from c:/dog.txt to c:/dog2.txt. But notice the final parameter: It’s the word TRUE in all capitals. What’s that? That’s a preprocessor macro defined somewhere in the bowels of the Windows header files.
You have to use either TRUE or FALSE when calling any of the Windows functions. That’s because in the old days of C, when the early versions of Windows were invented, no bool type existed. Those resourceful people of the late 20th century had to define their own TRUE and FALSE as integers (usually either 1 and 0, respectively, or 0 and 1, respectively).
And by the way, that final parameter in CopyFile tells the function what to do if the file you’re copying to already exists: TRUE means don’t overwrite the existing file; just abort. FALSE means overwrite it.
When a program runs, the data is in the memory but when it ends or the computer shuts down, it gets lost. To keep data permanently, we need to write it in a file.
File is used to store data. In this topic, you will learn about reading data from a file and writing data to the file.
fstream is another C++ standard library like iostream and is used to read and write on files.
These are the data types used for file handling from the fstream library:
C++ Create A File
| Data type | Description |
|---|---|
| ofstream | It is used to create files and write on files. |
| ifstream | It is used to read from files. |
| fstream | It can perform the function of both ofstream and ifstream which means it can create files, write on files, and read from files. |
Opening a file
We need to tell the computer the purpose of opening our file. For e.g.- to write on the file, to read from the file, etc. These are the different modes in which we can open a file.
| Mode | Description |
|---|---|
| ios::app | opens a text file for appending. (appending means to add text at the end). |
| ios::ate | opens a file for output and move the read/write control to the end of the file. |
| ios::in | opens a text file for reading. |
| ios::out | opens a text file for writing. |
| ios::trunc | truncates the content before opening a file, if file exists. |
How To Make A Text File In Dev C++
Let's look at the syntax of opening a file.
C++ Text To File
We have opened the file 'example.txt' to write on it. 'example.txt' file must be created in your working directory. We can also open the file for both reading and writing purposes. Let's see how to do this:
Closing a file
C++ automatically close and release all the allocated memory. But a programmer should always close all the opened files. Let's see how to close it.
Reading and writing on a file
Cmd Create Text File
We use << and >> to write and read from a file respectively. Let's see an example.