GitHub Actions: Split Long Command into Multiple Lines

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

Additionally, you can append a block chomping indicator, -, + or none. which will alter the newlines at the end of the block.

these are the block chomping definitions

• - is called strip removes newlines at the end
• + is called keep keeps all newlines at the end
• default behavior is keeping a single newline at the end

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

Edit: @Connor Clark below suggests making sure that each line has the same indentation.

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: bash

RIGHT:

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

At the time this answer was originally written, this was not possible using backslashes. 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.

This is another way to do it, it will work with Github Actions:

name: build

on: [push]

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

alternative to the && is to split that in several steps, like:

name: build

on: [push]

jobs:
    build:
        runs-on: ubuntu-18.04
        steps:
            - name: Install Prerequisites - checkout phase
              uses: actions/checkout@v1

            - name: Install Prerequisites - update phase
              run: sudo apt-get update

            - name: Install Prerequisites - install phase
              run: >
                sudo apt-get install -y --no-install-recommends
                "a very very long
                list of prerequisites"