There may be times where a file of an exact size is needed to test file transfer speeds, upload limitations, etc. Here’s a script that will prompt for the size in MB and name of a file, and then create one. This is handy to add to your .bash_functions for quick access.

To create a file of a specific size and name using the dd command, you can use the following syntax:

dd if=/dev/zero of=<filename> bs=<blocksize> count=<number of blocks>

Here’s what each of the options mean:

  • if=/dev/zero: This specifies the input file as /dev/zero, which is a special file that provides an endless stream of null bytes.
  • of=<filename>: This specifies the output file name.
  • bs=<blocksize>: This specifies the block size in bytes. For example, if you want to create a file of size 1GB, you can set the block size to 1MB (1024 * 1024 bytes).
  • count=<number of blocks>: This specifies the number of blocks to be written. The total size of the file will be bs * count.

Here’s an example command to create a file named testfile of size 1GB:

dd if=/dev/zero of=testfile bs=1M count=1024

Note that the dd command can be dangerous if used incorrectly, as it can overwrite data on your disk. Make sure you double-check the command before running it.Sure, here’s an example script that asks the user for the size in MB and the name of the file, and then uses the dd command to create the file:


# Ask the user for the size in MB
read -p "Enter the size of the file in MB: " size_mb

# Ask the user for the file name
read -p "Enter the name of the file: " filename

# Calculate the block size and number of blocks

# Use dd to create the file
dd if=/dev/zero of="$filename" bs="$block_size" count="$num_blocks"

This script first prompts the user to enter the size of the file in MB and the name of the file. It then calculates the block size as 1MB and the number of blocks as the size in MB entered by the user. Finally, it uses the dd command to create the file with the specified name and size.