C++ || Snippet – How To Create A File Of Any Size

October 04, 2013 admin No comments

The following is sample code which demonstrates how to create a file of any size using the fseek and fwrite function calls.





		
		
			Create A File Of Any Size
			
C++
			
			// ============================================================================
//    Author: K Perkins
//    Date:   Oct 4, 2013
//    Taken From: http://programmingnotes.org/
//    File:  createfileN.cpp
//    Description: Demonstrate how to create a file of any size
// ============================================================================
#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cstring>
using namespace std;

int main(int argc, char* argv[])
{
    // declare variables
    int fileSize = 0;
    FILE* fp = NULL;

    // check the command line arguments
    if(argc < 3)
    {
        cerr<<"n** ERROR NOT ENOUGH ARGS!n"
            <<"nUSAGE: "<<argv[0]<<" <FILE NAME> <FILE SIZE>nn";	
        exit(1);
    }   
        
    // convert the file size from string to integer
    fileSize = atoi(argv[2]);	

    // open the file to be created
    fp = fopen(argv[1], "w+");

    // make sure the file was created ok
    if(!fp)
    {
        perror("open error");
        exit(1);
    }

    // set the file marker to position N in the file (where N = file size)
    if(fseek(fp, fileSize - 1, SEEK_SET) < 0)
    {
        perror("fseek error");
        exit(1);
    }
        
    // write a single byte to the file
    if(fwrite(" ", sizeof(char), strlen(" "), fp) < 0)
    {
        perror("write error");
        exit(1);
    }

    // close the file
    fclose(fp);
        
    return 0;
}// http://programmingnotes.org/
			
				
					
				
					1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
				
						// ============================================================================
//    Author: K Perkins
//    Date:   Oct 4, 2013
//    Taken From: http://programmingnotes.org/
//    File:  createfileN.cpp
//    Description: Demonstrate how to create a file of any size
// ============================================================================
#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cstring>
using namespace std;
 
int main(int argc, char* argv[])
{
    // declare variables
    int fileSize = 0;
    FILE* fp = NULL;
 
    // check the command line arguments
    if(argc < 3)
    {
        cerr<<"n** ERROR NOT ENOUGH ARGS!n"
            <<"nUSAGE: "<<argv[0]<<" <FILE NAME> <FILE SIZE>nn";	
        exit(1);
    }   
        
    // convert the file size from string to integer
    fileSize = atoi(argv[2]);	
 
    // open the file to be created
    fp = fopen(argv[1], "w+");
 
    // make sure the file was created ok
    if(!fp)
    {
        perror("open error");
        exit(1);
    }
 
    // set the file marker to position N in the file (where N = file size)
    if(fseek(fp, fileSize - 1, SEEK_SET) < 0)
    {
        perror("fseek error");
        exit(1);
    }
        
    // write a single byte to the file
    if(fwrite(" ", sizeof(char), strlen(" "), fp) < 0)
    {
        perror("write error");
        exit(1);
    }
 
    // close the file
    fclose(fp);
        
    return 0;
}// http://programmingnotes.org/

QUICK NOTES:
The highlighted lines are sections of interest to look out for.

The code is heavily commented, so no further insight is necessary. If you have any questions, feel free to leave a comment below.

The following is sample output:

./createfileN createfile.txt 12
[FILE "createfile.txt" IS CREATED AND IS 12 BYTES IN SIZE]

Was this article helpful?

👍 YesNo

Posted in: Advanced, C++, C++ Tags: cpsc 351, fseek, fwrite, unix

C++ || Snippet – How To Create A File Of Any Size

Related

Leave a ReplyCancel reply

Search

Compile Your Code Now

Translate Page

Popular Pages

Recent

Archives

Categories