Github Action: Split Long Command into Multiple Lines

I have a Github action command that is really long:

name: build

on: [push]

jobs:
    build:
        runs-on: ubuntu-18.04
        steps:
            - uses: actions/checkout@v1
            - name: Install Prerequisites
              run: |
                sudo apt-get update
                sudo apt-get install -y --no-install-recommends "a very very long list of prerequisites"

May I know whether it is possible to split the long command into multiple lines for better readability? I have tried the separator '' but it does not work. Thanks in advance.

I have a multi line command using backslash to separate the lines as follows:

- name: Configure functions
  run: |
    firebase functions:config:set \
      some.key1="${{ secrets.SOME_KEY_1 }}" \
      some.key2="${{ secrets.SOME_KEY_2 }}" \
    ...    

Note the preceding '|' character.

You can use the YAML folded style with > which is supported by GitHub Actions.

For example,

run: >
  xvfb-run
  ./mvnw -f my/pom.xml
  clean verify
  -DskipTests

newlines will be replaced with spaces so the above is equivalent to

run: xvfb-run ./mvnw -f my/pom.xml clean verify -DskipTests

Going to share this in since it has not been mentioned.

You can use:

• | called a Literal Block Scalar which preserves new lines and trailing spaces
• > called a Folded Block Scalar which converts new lines into spaces
• plain old strings, either unquoted, single-quoted or double-quoted

I found the site yaml-multiline.info useful for understanding how yaml strings are interpreted.

For my use case, I ended up doing the following:

run: >-
  for i in $(find . -type f -name "*.log");
  do
   echo "File: ${i} \n";
   cat $i;
   printf '%*s\n' "${COLUMNS:-$(tput cols)}" '' | tr ' ' -;
  done

The above answers all had pieces, but this is what worked for me in a github composite action. It should work in a regular workflow too.

As @lorenzo-bettini said, if you want everything to be on one line, use what @Josue Alexander Ibarra called a Folded Block Scalar.

run: >
  xvfb-run
  ./mvnw -f my/pom.xml
  clean verify
  -DskipTests

> newlines will be replaced with spaces so the above is equivalent to

run: xvfb-run ./mvnw -f my/pom.xml clean verify -DskipTests

If you want new lines to be preserved, use what @Josue Alexander Ibarra called a Literal Block Scalar.

run: |
  FILE=./package.json
  if test -f "$FILE"
  then
    echo "$FILE exists."
  else
    echo "File does not exist"
  fi

When you do a multi-line run, though, you have to make sure you indent correctly, otherwise step will think that shell: bash is part of the run: | string.

WRONG:

  steps:
    - run: |
      FILE=./package.json
      if test -f "$FILE"
      then
        echo "$FILE exists."
      else
        echo "File does not exist"
      fi
      shell: run

RIGHT:

  steps:
    - run: |
        FILE=./package.json
        if test -f "$FILE"
        then
          echo "$FILE exists."
        else
          echo "File does not exist"
        fi
      shell: run

This was not possible using backslashes, earlier. See the accepted answer on how to do it now.

---

As far as I know, GitHub Actions does not support that.

However, you can use environment variables for that.

For example, this script splits your command in 3 lines of code and executes it as one line.

steps:
  - name: Install Prerequisites
    run: |
      sudo apt-get update
      bash -c "$line1 $line2 $line3"
    env:
    - line1='sudo apt-get install -y --no-install-recommends '
    - line2='a very very long list'
    - line3='of prerequisites'

It creates the environment variables line1, line2 and line3 and concats and executes them in a bash session.

Note also the join and format functions for expressions:

HELLO_WORLD = ${{ join('Hello', 'world!') }}
HELLO_WORLD = ${{ format('{{Hello {0}}}', 'World') }}

Presumably these could be combined with env variables.