Additional function(s): lowercase|uppercase #25768

DazWilkin · 2020-10-29T19:41:17Z

DazWilkin
Oct 29, 2020

Noob GitHub Actions user here.

My GitHub username includes uppercase characters.

My first GitHub Actions workflow builds a container image to push to GitHub Container Registry.

Container registries require lowercase repo names.

I wanted to be able to:

tags: ghcr.io/${{ github.repository }}:${{ github.sha }}

But this errors because github.repository_owner includes uppercase.

I was unable to find a function nor any other way to pipe this value into lowercase and think such a function (and perhaps its companion uppercase) would be useful.

tags: ghcr.io/${{ lowercase(github.repository) }}:${{ github.sha }}

Or, is there a better way to achieve this?

env:
  REPO: my-username/some-repo
...
steps:
   ...
   tags: ghcr.io/${{ env.REPO }}:${{ github.sha }}

Answered by airtower-luna

Oct 29, 2020

The env approach is what I’d do, except that I’d use Bash parameter expansion to convert the case instead of hardcoding it:

      - name: downcase REPO
        run: |
          echo "REPO=${GITHUB_REPOSITORY,,}" >>${GITHUB_ENV}

Or if you need the tag in a run step you could do the parameter expansion right there.

View full answer

airtower-luna · 2020-10-29T20:41:32Z

airtower-luna
Oct 29, 2020

The env approach is what I’d do, except that I’d use Bash parameter expansion to convert the case instead of hardcoding it:

      - name: downcase REPO
        run: |
          echo "REPO=${GITHUB_REPOSITORY,,}" >>${GITHUB_ENV}

Or if you need the tag in a run step you could do the parameter expansion right there.

2 replies

bergus Jan 8, 2024

Imo it's slightly nicer to use the (new-ish) operator syntax of bash:

echo "REPO=${GITHUB_REPOSITORY@L}" >> "${GITHUB_ENV}"

U
The expansion is a string that is the value of parameter with lowercase alphabetic characters converted to uppercase.

u
The expansion is a string that is the value of parameter with the first character converted to uppercase, if it is alphabetic.

L
The expansion is a string that is the value of parameter with uppercase alphabetic characters converted to lowercase.

Likqez Apr 12, 2024

When you write a variable definition to GITHUB_ENV, subsequent steps will have it as an environment variable. For example

See here.

Simran-B · 2020-10-29T21:28:01Z

Simran-B
Oct 29, 2020

While using built-in shell functionality is probably more succinct, you could also use a string manipulation action if you want something that works the same regardless of the shell type:

    steps:
      - id: string
        uses: ASzc/change-string-case-action@v1
        with:
          string: ${{ github.repository }}
      - run: |
          echo "${{ steps.string.outputs.lowercase }}"

1 reply

Entepotenz Dec 30, 2022

I wrote an alternative to the ASzc/change-string-case-action version.
https://github.com/Entepotenz/change-string-case-action-min-dependencies

It is using pure python for the string conversion.
It does not depend on any library and therefore does not require any maintenance from security perspective :-)
Additionally I have a couple of tests running automatically before publishing.

ArnoudAtBreenservices · 2021-06-04T13:03:04Z

ArnoudAtBreenservices
Jun 4, 2021

How would you use it inside the run step, then?

0 replies

airtower-luna · 2021-06-04T14:48:16Z

airtower-luna
Jun 4, 2021

When you write a variable definition to GITHUB_ENV, subsequent steps will have it as an environment variable. For example:

      - name: downcase REPO
        run: |
          echo "REPO=${GITHUB_REPOSITORY,,}" >>${GITHUB_ENV}
      - name: use REPO
        run: echo "The value of REPO is: ${REPO}"

0 replies

FrostyLeaf · 2021-12-31T10:34:50Z

FrostyLeaf
Dec 31, 2021

The following commands can do this trick:

ABC=$(echo 'console.log("abc".toUpperCase())' | node -);
echo $ABC

In you case, it could be:

repo=$(echo 'console.log("${{ github.repository }}".toLowerCase())' | node -)
tags: ghcr.io/${repo}:${{ github.sha }}

1 reply

ystxn Jan 11, 2023

the reply before you already provided the most succinct solution. your response is confusing in suggesting that it's possible to run script within a step and interpret the value within a field in the same step, which is not possible.

FrostyLeaf · 2021-12-31T10:45:03Z

FrostyLeaf
Dec 31, 2021

Python also does the exactly same thing:

ABC=$(echo 'print("abc".upper())' | python3.9 -)
echo $ABC

0 replies

Entepotenz · 2023-01-13T21:41:02Z

Entepotenz
Jan 13, 2023

IMHO:
I would feel uncomfortable running those bash commands basically calling eval in python or nodejs.

I am talking about those examples:

ABC=$(echo 'print("abc".upper())' | python3.9 -)
echo $ABC

ABC=$(echo 'console.log("abc".toUpperCase())' | node -);
echo $ABC

I think those two links describe much more secure solutions:

You can also check out the security best practices for GitHub actions: https://res.cloudinary.com/da8kiytlc/image/upload/v1651737641/GitHub-Actions-Security-Best-Practices_cheatsheet.pdf

0 replies

d3vpasha · 2023-10-19T14:07:06Z

d3vpasha
Oct 19, 2023

I don't like any answer above, for me, Github actions must have some built-in functions to do usual things like uppercase, camelcase, lowercase, etc..

0 replies

shellscape · 2023-11-24T19:41:57Z

shellscape
Nov 24, 2023

See this answer https://stackoverflow.com/a/63315136/416845 on how to use ${var^^} to uppercase

0 replies

ALERTua · 2024-01-08T18:08:57Z

ALERTua
Jan 8, 2024

These worked for me:

      - name: lowercase github.repository
        run: |
          echo "IMAGE_NAME=`echo ${{github.repository}} | tr '[:upper:]' '[:lower:]'`" >>${GITHUB_ENV}

      - name: lowercase github.repository
        run: |
          echo "IMAGE_NAME=${GITHUB_REPOSITORY@L}" >> ${GITHUB_ENV}

then ${{ env.IMAGE_NAME }} or "${{ env.IMAGE_NAME }}:latest"

0 replies

bergus · 2024-01-08T23:31:36Z

bergus
Jan 8, 2024

See also https://github.com/orgs/community/discussions/10553

0 replies

lordfolken · 2024-02-06T22:57:54Z

lordfolken
Feb 6, 2024

None of these answers solve the actual problem.
If you want to run steps inside an image, then you need to first to be able to specify the image path, in order to pull the image.
Without variable expansion, an additional job is necessary that first lowercases the variable and then using that in a subsequent container job.
What a waste of resources.

1 reply

esaporski Apr 2, 2024

GitHub Actions has a lot of potential, but right now it feels like a half-finished product.

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