First simple version of Github Action

README.md

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+# Verify File Checksum action
+
+This action verifies the checksum of a given file. If it passes, the Github Action passes.
+
+## Inputs
+
+### `file`
+
+**Required** The file to check. If it's an URL, use the [`file:`](https://en.wikipedia.org/wiki/File_URI_scheme) protocol.
+
+### `checksum`
+
+**Required** The expected (hexadecimal) checksum of the given file.
+
+### `algorithm`
+
+**Required** The algorithm that has been used for calculating the checksum. Run `openssl list-message-digest-algorithms` in your terminal to check all available algorithms. Examples: `MD5`, `SHA512`, `DSA-SHA1`.
+
+## Outputs
+
+### `verify-result`
+
+Does the checksum match with the given file.
+
+## Example usage
+
+```yaml
+uses: actions/[email protected]
+with:
+  file: 'file://assets.iec.ch/public/tc57/IEC_61850-6.2018.SCL.2007B4.full.zip'
+  checksum: 'd61da94836ff974fbd781ad1bc967039'
+  algorithm: 'MD5'
+```

action.yml

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+name: 'Verify File Checksum'
+description: 'Verify the checksum of a given file. If it passes, the Github Action passes.'
+inputs:
+  file:
+    description: 'The file to check.'
+    required: true
+  checksum:
+    description: 'The expected checksum of the given file.'
+    required: true
+  algorithm:
+    description: 'The algorithm that has been used for calculating the checksum.'
+    required: true
+    default: 'MD5'
+outputs:
+  verify-result:
+    description: 'Does the checksum match with the given file.'
+runs:
+  using: 'node12'
+  main: 'index.js'

index.js

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+const core = require('@actions/core');
+const github = require('@actions/github');
+const crypto = require('crypto');
+const fs = require('fs')
+
+try {
+    // Create a Hash based on the given algorithm.
+    const hashAccordingGivenAlgorithm = crypto.createHash(core.getInput('algorithm'));
+
+    // Calculating checksum for given file.
+    const streamGivenFile = fs.createReadStream(core.getInput('file'));
+    const calculatedChecksum = hashAccordingGivenAlgorithm.update(streamGivenFile).digest('hex');
+
+    const expectedChecksum = core.getInput('checksum');
+
+    console.log(`Calculated checksum: ${calculatedChecksum}`);
+    console.log(`Expected checksum: ${expectedChecksum}`);
+
+    if (calculatedChecksum == expectedChecksum) {
+        core.setOutput("verify-result", "Checksums are equal");
+    } else {
+        core.setOutput("verify-result", "Checksums are not equal");
+        core.setFailed(error.message);
+    }
+} catch (error) {
+    core.setFailed(error.message);
+}