How to create a file with a given size in Linux?

Question

For testing purposes I have to generate a file of a certain size (to test an upload limit).

What is a command to create a file of a certain size on Linux?

Answer 1

Some of these answers have you using /dev/zero for the source of your data. If your testing network upload speeds, this may not be the best idea if your application is doing any compression, a file full of zeros compresses really well. Using this command to generate the file

 dd if=/dev/zero of=upload_test bs=10000 count=1

I could compress upload_test down to about 200 bytes. So you could put yourself in a situation where you think your uploading a 10KB file but it would actually be much less.

What I suggest is using /dev/urandom instead of /dev/zero. I couldn't compress the output of /dev/urandom very much at all.