Create a 2Mb file

Hi,
Happy new year.

Thanks for your answers to my questions during 2022.

How can I create a 2Mb file?

Thanks

With
mkfile ...
or
dd if=/dev/zero ...

Consult the respective man pages!

Thank you,
dd is to convert:
dd Command

Purpose

   Converts and copies a file.

$ man mkfile
Manual entry for mkfile not found or not installed.

Thanks.

This is true since 'dd' has an 'if' (input file) argument and an 'of' (output file) argument.

So as already suggested, using /dev/zero is a special 'file' of just zeros.

So you can use that as input file,

if=/dev/zero

Output file will be the file that you want to write,

of=<path to output file>

You control the output file size with two argments, bs= and count=

'bs' (blocksize) is the blocksize that you want to read and write, and would typically be specified as 512 bytes since that is typical disk sector size,

'count' specifies how many blocks you want to write. NOTE: Without 'count' the command will continue forever thereby filling your filesystem eventually.

So,

bs=512 count=4000

will give you exactly 2MB. (512 * 4000)

Or
bs=1024 count=2000
Or
bs=1024 count=2048
?

This truncate command creates a file of 2MB instantly.

It is a "sparse file". If you read it, it contains 2097152 zero bytes. But it occupies no space on the disk. So if you want a large file for e.g. performance checking, the results will be misleading.

I can create a 2 terabyte sparse file on my 300 megabyte disk, and that takes zero blocks too.

$ truncate -s $(( 2 * 1024 * 1024 )) EmptyFile
$ ls -l EmptyFile
-rw-rw-r-- 1 paul paul 2097152 Jan  2 22:46 EmptyFile
$ wc EmptyFile
      0       0 2097152 EmptyFile
$ file EmptyFile
EmptyFile: data
$ stat  EmptyFile
  File: EmptyFile
  Size: 2097152   Blocks: 0   IO Block: 4096   regular file
Device: 809h/2057d	Inode: 6165481     Links: 1
Access: (0664/-rw-rw-r--)  Uid: (1000/paul)   Gid: (1000/paul)
Access: 2023-01-02 22:46:45.953861059 +0000
Modify: 2023-01-02 22:46:27.786605625 +0000
Change: 2023-01-02 22:46:27.786605625 +0000
 Birth: -
$ 

instead of calculating the number of bytes, you could simply write

$ truncate -s 2m file

Yes. Thank you. It worked.

Here is the answer by ChatGPT after I copied-and-pasted the original question to ChatGPT:

To create a 2 MB file, you can use a text editor such as Notepad on Windows or TextEdit on Mac to create a large file by adding text or by repeating a smaller file multiple times. Here is an example of how to do this using the cat command in a terminal or command prompt on a Unix-like system such as Linux or macOS:

1. Open a terminal window.
2. Use the dd command to create a 1 MB file filled with random data: dd if=/dev/urandom of=1MB.txt bs=1M count=1
3. Use the cat command to create a new file by concatenating the 1 MB file twice: cat 1MB.txt 1MB.txt > 2MB.txt

This will create a new file called 2MB.txt that is 2 MB in size. Note that the actual content of the file will be random data.

You can also use a file compression tool to create a 2 MB file by compressing a larger file. For example, you could use the gzip command to compress a text file and create a smaller .gz file.

I hope this helps! Let me know if you have any other questions.

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