How to use 0/10 in cron in a yaml file?

Question

I'm trying to use a cron job referenced in a yaml file part as part of my CircleCI CI system:

I would like a job to run every 10 mins using the 0/10 * * * * format but I get:

Config does not conform to schema

So how to use 0/10 in cron in a yaml file?`

Using a valid cron expression:

https://crontab.guru/#0/10_*_*_*_*

I get

Config does not conform to schema: 
{:workflows {:hourly {:triggers [{:schedule {:cron (not (:circleci.specs.cron/posix-expr \"0/10 * * * *\"))}}]}}}

I tried various format such as

cron: "0/10 * * * *"
cron: 0/10 * * * *
cron: "0\/10 * * * *"
cron: 0\/10 * * * *

but none were valid for allowing the slash.

Rest of section for context:

  hourly:
    triggers:
      - schedule:
          cron: "0/10 * * * *"
          filters:
            branches:
              only:
                - master
                - circleci-project-setup:

Answer 1

The docs say

cron key is defined using POSIX crontab syntax.

The linked manpage does not specify /. It is non-standard and apparently not supported. Wikipedia says that

POSIX does not define a use for slashes; its rationale (commenting on a BSD extension) notes that the definition is based on System V format but does not exclude the possibility of extensions

So you just can't use / here.

You can use the equivalent

"0,10,20,30,40,50 * * * *"

Answer 2

You can use > operator

So this example works for cron expression:

  schedule: >
     '*/3 * * * *'