Bytes, Linux, Creating files of any size

What?

How to create a file of any given size on linux

Why?

Quick testing, ballast, and dummy file creation.

How?

Create a single 100K file¹

truncate -s 100K testfile.bin

or

fallocate -l $((100*1024)) testfile.bin

Create a single 100K file filled with zeros

head -c 100K /dev/zero > testfile.bin

or

dd if=/dev/zero of=testfile.bin  bs=100K  count=1

or

dd if=/dev/zero of=testfile.bin  bs=1K  count=100

on Mac, use:

# prefers lowercase
dd if=/dev/zero of=testfile.bin  bs=100k  count=1

Create a single 100K file filled with random bytes

head -c 100K /dev/random > testfile.bin

or

dd if=/dev/random of=testfile.bin  bs=100K  count=1

or

dd if=/dev/random of=testfile.bin  bs=1K  count=100

on Mac, use:

# prefers lowercase
dd if=/dev/random of=testfile.bin  bs=100k  count=1

Footnotes

1. Note that a truncated file may not necessary have the real space allocated to it and therefore will be subject to certain optimizations with respect to syscalls that may not apply to other file types. ↩