C Programming Lesson - File Copy Program in C

Today we are going to learn a simple file copy program in C language. As I said this is a simple file copy program so you should not expect its output like DOS copy command has. Ok let’s start.

The main logic behind this program is that we will open a file and copy its contents to new file character by character. So we are going to implement logic that we had used, especially as a student, in our school or college i.e. copying note from a friends’ notes.

For this purpose we will need two files, one source file and other will be new file. Source file will be opened in read- only mode because we are not going to modify any data of this file, we only need to read character. Newly created file will be opened in write mode because we need to write every data what we will find in source file.

#include<stdio.h>
#include<conio.h>
#include<stdlib.h>

void main(int arg,char *arr[])
{
	FILE *fs,*ft;
	char ch;
	clrscr();
	if(arg!=3)
	{
	printf("Argument Missing ! Press key to exit.");
	getch();
	exit(0);
	}

	fs = fopen(arr[1],"r");
	if(fs==NULL)
	{
	printf("Cannot open source file ! Press key to exit.");
	getch();
	exit(0);
	}

	ft = fopen(arr[2],"w");
	if(ft==NULL)
	{
	printf("Cannot copy file ! Press key to exit.");
	fclose(fs);
	getch();
	exit(0);
	}

	while(1)
	{
	ch = getc(fs);
	if(ch==EOF)
	{
	break;
	}
	else
	putc(ch,ft);
	}

	printf("File copied succesfully!");
	fclose(fs);
	fclose(ft);
}

Important Note

NOTE : Please don't save this program as "copy.c" otherwise it will not work. You can name it copyfile.c etc. I named it copyf.c.

Code Explanation

As you can see this program is not for those who has just began C programming in their school or college. This is for those who have idea of file handling, function, pointer, array etc. So I’m not going to explain it line by line, only which I think is important will be explained.

Line – 5: This line is starting of the main function which accepts two arguments or parameters. First argument is an integer argument in the main function which stores the number of parameters provided at the runtime. In our program it has to be 3 (e.g. program_name source_file destination_file). Second argument in main function is a character array pointer, as you can see, which store the arguments.

Line – 7: This line declares two file pointer variables which we will need in our program. One file pointer variable will be used to read file and another will be used to write to file.

Line – 10-15: These line will check whether user has provided 3 arguments or not. If argument is less than 3 or greater than 3, then it will show error message.

Line – 17-23: In these lines we will open source file in read mode. To serve this purpose we will use “fopen()” function. This function requires two arguments, first is file name and second is file opening mode. It takes file name from “main()” function’s character array pointer argument. If “fopen()” function can open file successfully then returns pointer else returns NULL. We are checking this, if file is not found or file cannot be accessed due to security restriction then there is no need to execute program further.

Line – 25-32: In this block of code we are trying to create a new file. So we need to open this file in write mode. It also takes file name from “main()” function’s character array pointer argument. If fopen() function returns NULL then we need to close source file stream and exit program.

Line – 34-43: As you can see here we have declared an infinite while loop and the loop continues until end of file is reached. The “gets()” function reads character from given stream and stores character in ch variable then increments file pointer to next character. In line 42 we are writing character stored in ch variable to new file (ft file pointer) with the help of “putc()” function.

Line – 46-47: These two lines contain two same functions whose job is to clearing the stream buffer and closing the stream buffer. Because we are using two file pointer, so we need to close both of them.

I know this explanation is very concise for those who are new in file handling in C. But you can ask question about this topic through comment provided below. Thank you, keep visiting me.

Best books on C Language

Program Output

To run program properly you need to execute this program from DOS shell.
To run program properly you need to execute this program from DOS shell.
Successful completion of copy file.
Successful completion of copy file.

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Comments 21 comments

hAkUwoH123 7 years ago

bubu ang sagot mo!!!!


James 7 years ago

This was very helpful. Thank You. I am creating a function library for a low-level system and I do not need to use system calls, and this example needs a little modification on my part, but it helped put me on the right track. Thanks again.


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ciidoctor 7 years ago

thank you


Shawn Smith 6 years ago

Could you possibly write a program that is more incorrect? It's pretty tough here.

Error 1: The main() function in a C program always returns an "int," never "void." Take a look at the specification to see what I mean, and never, never, ever use Herbert Schildt as a reference.

Error 2: exit() is declared in , (which you failed to include) and it takes an int as a parameter. You used it incorrectly every time.

Error 3: getc() returns an int, not a char. If the source file happens to have a chr(255) in it (maybe it's an executable), your program will see that as the end (because it will get converted to an integer -1, which equals EOF) and exit prematurely.

Error 4: You don't check the return status of getc(), putc(), or the fclose()s, all of which can fail, but your program will report everything is a-ok.

Error 5: Not putting a newline at the end of your final printf means that the next prompt will appear in a really ugly place.

Error 6: Why no including when you're using getch()? And, by the way, getch() is a microsoft specific function, with no guarantees of being available on other platforms.

Please correct these errors so you don't make other novices look stupid when they cite your examples.


sravan 6 years ago

it is very good indeed!


ducalty 6 years ago

oiiiiiiiiiii ha ha ha


jignesh 6 years ago

data type in c language : your sourse code in you're internet


NoName 5 years ago

I can't agree with what Shawn Smith said more.

The author "should" read more examples from the programming text book but post a piece of "not very correct" code to misguide beginners.


N4D13 5 years ago

Using getc() to copy files is insecure and slow, open files as binary and use fread(),fwrite() and memset().


akshaya 5 years ago

plz include more examples


JINAL 5 years ago

Really Good..:)


raj_sty 5 years ago

May be this will replace the data in destination file if any file contained in it...can u tell me how to append the contents of one file to the begining of the other file


Isaac 5 years ago

Plz am new in programming and also to file handling..plz can u help me here..hw to include a program and and then save it plz...am reaaly lost here

FILE *fs,*ft;

char ch;

clrscr();

if(arg!=3)

{

printf("Argument Missing ! Press key to exit.");

getch();

exit(0);

}


Avinash 5 years ago

Nice!


ramakrishna 5 years ago

why we can use FILE in capitals


Rohit Agarwal 5 years ago

@isaac the particular part of that program is used to check the number of command line argument only


Mohammed 4 years ago

can anybody tel me the difference between two types of file inclusion ..one using less than and greater to sign and other using ""


code dude 4 years ago

You use "" when doing an include when you are including a header file you make yourself. You use the LESS THAN and GREATER THAN when you are including a header file that is a standard one someone like Microsoft made.


Dilip Bheda 4 years ago

Hello Rajkishor,

I just tried out your code to copy any file to network path(LAN).

It is working with simple text file properly but not with audio or video files. It reach to EOF very early, so not able to copy all data in your below code.

while(1)

{

ch = getc(fs);

if(ch==EOF)

{

printf("End of File!");

break;

}

else

putc(ch,ft);

}

So I changed it as below :

while(!feof(fs))

{

ch = getc(fs);

putc(ch,ft);

}

Now it is working very well.

Nice code to understand. I like it.


shekhar 4 years ago

i like this dite much


rajeswara dora 4 years ago

really very much easy to undrstand

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