Create large files bash

I guess the thing with the "cat" approach is that it grows exponentially. On starting the second iteration, 'newfile' already has 1 line and 'file' has 2, and when it is done, 'newfile' is now 3 lines and 'file' is 5. Next, 'newfile' will be 8 and 'file' will be Next 21, 34 , etc.

If you have truncate around, you can truncate -s 1G to create the file in first place. MelBurslan MelBurslan 6, 2 2 gold badges 21 21 silver badges 34 34 bronze badges. Apart from forgetting the. Sign up or log in Sign up using Google. Sign up using Facebook. Sign up using Email and Password. Post as a guest Name. Email Required, but never shown. The Overflow Blog. Podcast Making Agile work for data science.

Stack Gives Back Featured on Meta. New post summary designs on greatest hits now, everywhere else eventually. Linked Related 9. The truncate command supports all modern file systems. The fallocate command allocates all of the space to the file without writing a single byte of data in the file.

It means, if you use the fallocate command to create a 20GB file, you will get a file that consumes 20GB actual disk space but contains no data. The truncate command creates a sparse file instead of the actual file. The difference between a sparse file and an actual file is that a sparse file doesn't consume all allocated space. It only consumes the space that is used by data. For example, you created two 50GB files; one from the fallocate command another from the truncate command.

The first file immediately consumes all allocated 50GB space while the second file consumes only the space that is required by the actual data. Since the truncate command does not put any data in the file, the actual consumed disk space remains unchanged. Let's take one more example. Suppose you have 5 GB disk space and you want to create a file of 10GB for testing.

Since the fallocate command allocates all assigned space immediately, you can't create a file of 10GB if you only have 5GB disk space.

In this case, you can use the truncate command. Since the truncate command creates the sparse file and a sparse file does not consume any disk space until it contains any data, you can easily create a file of 10GB for testing even if you only have 5GB disk space. For example, the following commands generate 5GB named 5-gb-file and 80GiB named gib-file files respectively. For example, the following command generates GB named gb-file and 10GiB named gib-file files respectively.

If you want to create an empty file or a zero size file, you can use the touch command. The touch command, use the following syntax. Email Required, but never shown. The Overflow Blog. Podcast Making Agile work for data science. Stack Gives Back Featured on Meta. New post summary designs on greatest hits now, everywhere else eventually.

Linked Related Hot Network Questions. Question feed. Stack Overflow works best with JavaScript enabled. Accept all cookies Customize settings. Firstly, to get the obvious out of the way.

This is a special file on Linux that provides a null character every time you try to read from it. This means we can use it along with the dd command to quickly generate a file of any size. This file will not contain any lines i. The disadvantage is the fact that the file will only contain null characters and as a result will not seem to contain any lines. The command is similar:. To generate a Mb file we would do:.