31

31 is a simple tool you can use to run code in the background on a server.

For example

31 c 'sleep 100; echo 2'

runs the command sleep 100; echo 2 in a screen session then sends you an email with the output of the command once it is complete.

Setup

Install 31 by running

pip install 31

Then set up your email address by running

31 config email youremail@example.com

Quick dependency setup

On ubuntu you can run

sudo apt install screen mailutils

to quickly set up the dependencies needed.

Detailed dependency setup

Mail program

By default, 31 searches for a mail program to use from the following list. You can also force it to use one of the programs by using the command

31 config mail_program <mail program name>

• gnu_mail. To install on ubuntu you can run

sudo apt install mailutils

• mutt. To install on ubuntu you can run

sudo apt install mutt

Screen Manager

Currently 31 only supports screen. To install screen on ubuntu run

sudo apt install screen

Options

See 31 -h for a full list of options. This section covers only some of the more complicated ones

Foreach

This option allows you to run multiple commands with text substitution. As a basic usage example, the code

31 c -f %x 1,2,3 'touch %x.txt'

Creates each of the files 1.txt, 2.txt, and 3.txt. The variable substitution is managed via direct text-substitution, and thus your variables do not need to begin with %, this works equally well (though is far less readable)

31 c -f 2 1,2,3 'touch 2.txt'

You can also modify two variables in tandem like this:

31 c -f2 %x %ext 1,2,3 txt,png,py 'touch %x.%ext'

This creates the files 1.txt, 2.png, 3.py. If you instead want to create all combinations, you can run:

31 c -f %x 1,2,3 -f %ext txt,png,py 'touch %x.%ext'

This creates the files 1.txt, 1.png, 1.py, 2.txt, 2.png, 2.py, 3.txt, 3.png, 3.py.

The values field is in comma-separated-value form, which means you can use " as a CSV escape, as such:

31 -c -f %x '",",2' `touch %x.txt`

which creates the files ,.txt and 2.txt.