Apple - Time in milliseconds since epoch in the terminal

The date program in OS X is different than GNU's coreutils date program. You can install coreutils (including gnu-date), then you will have a version of date that supports milliseconds.

As the installation from source can be a hassle for native OS X users I advise you to use Homebrew.

To install these tools using Homebrew run this oneliner in your terminal:

ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install)"

Homebrew is now installed (it is wise to follow the installer's suggestions after installation). Now we will install coreutils using brew.

brew install coreutils

As the installation says, all commands have been installed with the prefix 'g' (e.g. gdate, gcat, gln, etc etc). If you really need to use these commands with their normal names, you can add a "gnubin" directory to your PATH (~/.bash_profile) like:

PATH="/usr/local/opt/coreutils/libexec/gnubin:$PATH"

You can now run

gdate +%s.%N

and this will output your time since the epoch in milliseconds.

In OS X, just run date +%s as OS X doesn't support any more precision than this in date's output and any excess precision not supported by the internal representation is truncated toward minus infinity.

If you want milliseconds output, you can use the following command, although the output is just corrected by appending zeros rather than adding precision due to the aforementioned reason. The following does output correct milliseconds on systems which support the necessary precision.

echo $(($(date +'%s * 1000 + %-N / 1000000')))

^{Source for above command: Unix.SE – How to get milliseconds since Unix epoch}

If you just want a command that appends the right number of zeros in OS X, you can use:

date +%s000

Perl is ubiquitous.

$ perl -MTime::HiRes=time -e 'printf "%.9f\n", time'
1557390839.244920969