Files

Engine offers several options for working with files and file systems. This article describes the file handling functionality available to you on the Engine platform.

Use Cases

You can use Engine file functionality to

• retreive files from a remote system and store them in Engine
• transfer files from Engine to remote systems
• send files as attachments of emails
• use files as templates for mails or messages

Concept

You can store binary content as files in Engine. Files can be accessed using the flow API. Several connectors directly read or write Engine files.

User Interface

The User Interface allows to upload and download files, and to view — and, for text files, edit — their content directly in the browser. What is shown adapts to the file's detected type (see Viewing file content below).

Content type detection

Whenever file content is written — an upload, a flow API save_*_content call, or a connector that stores a file — Engine detects the file's MIME content type server-side and stores it on the FILE record in the read-only content_type field. Detection is best-effort and resolves in this order:

1. an exact, extension-less file-name match (for example Dockerfile);
2. the file-name extension (an explicit map, then the standard mimetypes registry);
3. a text-versus-binary sniff of the content when name and extension are inconclusive.

The value is a canonical MIME string such as text/x-python, application/json, image/png, or application/octet-stream. Because it is stored on the record, every API, MCP, and flow-API consumer can adapt to a file's type — not only the Console. The field is computed by Engine and cannot be set directly.

example

Read a file's detected content type

import flow_api

def handler(system: flow_api.System, this: flow_api.Execution, inputs: dict):
    system.file('config.yaml').save_text_content('key: value\n')
    # content_type is detected and stored automatically on write
    this.log(system.file('config.yaml').get('content_type'))  # -> application/yaml
    return this.success('all done')

Viewing file content

The Console adapts how it displays a file's content to the detected content_type:

File type	Console display
Plain text, or a texty file with no dedicated grammar (text/plain, CSV, TOML, …)	Plaintext code editor (editable)
Source or structured text — Python, JSON, YAML, JavaScript, TypeScript, SQL, XML, HTML, Markdown, shell, Dockerfile, INI	Code editor with syntax highlighting
Images (image/png, image/jpeg, image/gif, image/webp, …)	Inline, size-capped image preview
Everything else — binary, PDF, audio, video, archives, and SVG	Download only: the file size and a download button are shown, with no inline render

note

SVG images are shown as download-only rather than rendered inline, because an SVG can embed scripts (a cross-site-scripting risk). Files whose content_type has not yet been detected — for example files created before this feature — fall back to the plaintext editor.

Large files are not loaded into the browser automatically. Two workspace configuration limits govern this:

• FILE_SIZE_BYTES_ALWAYS_LOAD_LIMIT — files up to this size are loaded and displayed automatically.
• FILE_SIZE_BYTES_OPTIONAL_LOAD_LIMIT — files larger than the always-load limit but up to this larger limit are not loaded automatically; you can choose to load them on demand.

Files larger than the optional-load limit are download-only regardless of their type.

Upload files

1. Click the "+ Create" button in the left hand menu and select "Upload file".

Buttons to upload files

2. In the dialog choose one or several files and confirm.
3. The upload progress is shown in the top bar.

The upload progress bar

4. Clicking on a file in the upload progress panel will open the file in the User Interface.

Download files

Click the "Download" button next to any file.

The download button

Flow API

The flow API provides methods to read and write file content as bytes, base64 string, or decoded as utf-8 string.

example

Create, write, read, list, and delete files

import flow_api

def handler(system: flow_api.System, this: flow_api.Execution, inputs: dict):
    # store a text (utf8 string)
    system.file('my-file.txt').save_text_content('text content')
    # read as base64
    assert system.file('my-file.txt').get_base64_content() == 'dGV4dCBjb250ZW50'
    # store bytes data
    system.file('my-file.dat').save_bytes_content(b'bytes data \xc3\xa4\xc3\xb6\xc3\xbc')
    # read as text (utf8 string)
    assert system.file('my-file.dat').get_text_content() == 'bytes data äöü'
    # store a base64 encoded string
    system.file('my-file.ext').save_base64_content('Q2xvdWRvbWF0aW9u')
    # read as bytes
    assert system.file('my-file.ext').get_bytes_content() == b'Cloudomation'

    # list files
    for file_ in system.files():
        this.log(file_.get('name', 'content_size_bytes'))

    # clean up
    system.file('my-file.txt').delete()
    system.file('my-file.dat').delete()
    system.file('my-file.ext').delete()

    return this.success('all done')

Connectors accessing files

SCP

The SCP connector allows to copy files using the SCP protocol.

example

Read and write a file using the SCP connector.

import flow_api

def handler(system: flow_api.System, this: flow_api.Execution, inputs: dict):
    # copy a file from a remote SCP host to Engine
    this.connect(
        'my-web-server',
        src='/var/log/apache2/access.log',
        dst='cloudomation:apache-access.log',
    )

    # access the file content
    content = system.file('apache-access.log').get_text_content()

    # copy a file from Engine to a remote SCP host
    this.connect(
        'my-web-server',
        src='cloudomation:index.html',
        dst='/var/www/html/index.html',
    )

    return this.success('all done')

SMB

The SMB connector allows to copy files using the SMB protocol.

example

Read and write a file using the SMB connector.

import flow_api

def handler(system: flow_api.System, this: flow_api.Execution, inputs: dict):
    # copy a file from a fileshare to Engine
    this.connect(
        'my-windows-host',
        src='share-name\\path\\to\\report.xlsx',
        dst='cloudomation:report.xlsx',
    )

    # copy a file from Engine to a fileshare
    this.connect(
        'my-windows-host',
        src='cloudomation:processing.log',
        dst='report-share\\processing.log',
    )

    return this.success('all done')

GIT

The GIT connector allows to fetch files from a repository and store them in Engine

example

Fetch files from git and store them in Engine

import flow_api

def handler(system: flow_api.System, this: flow_api.Execution, inputs: dict):
    this.connect(
        connector_type='GIT',
        command='get',
        repository_url='https://example.com/path/to/repo.git',
        ref='develop',
        files_path='files-from-repository'
    )

    # list files which were fetched
    for file_ in system.files(
            filter_={
                'field': 'name',
                'op': 'like',
                'value': 'files-from-repository/%',
            },
    ):
        this.log(file_.get('name', 'content_size_bytes'))
        # clean up
        file_.delete()

    return this.success('all done')

IMAP

The IMAP connector can store email attachments in Engine

example

Fetch an email and store the attachments in Engine

import datetime
import flow_api

def handler(system: flow_api.System, this: flow_api.Execution, inputs: dict):
    # search for todays messages with "report" in the subject line
    today = datetime.date.today().strftime('%d-%b-%Y')
    message_ids = this.connect(
        'my-imap-server',
        name='search for mails',
        command='search',
        folder='INBOX',
        criteria=[
            'SUBJECT', 'report',
            'SINCE', today,
        ],
    ).get('output_value')['result']
    messages = this.connect(
        'my-imap-server',
        name='fetch mails',
        command='fetch',
        message_set=message_ids,
        # attachments are stored as `{message-id}-{attachment-file-name}`
        store_attachments=True,
    ).get('output_value')['result']

    # list all attachments which were fetched
    for message_id in message_ids:
        for file_ in system.files(
                filter_={
                    'field': 'name',
                    'op': 'like',
                    'value': f'{message_id}-%',
                },
        ):
            this.log(f'attachment of message {message_id}: {file_.get("name")})

    return this.success('all done')

SMTP

The SMTP connector allows to send mails with attachments from Engine files.

example

Send a mail with attachment

import flow_api

def handler(system: flow_api.System, this: flow_api.Execution, inputs: dict):
    this.connect(
        'my-smtp-server',
        from='no-reply@example.com',
        to='user@example.com',
        subject='monthly report',
        text='the monthly processing report is attached',
        attachments=[
            # attach files from the Engine files resource
            'cloudomation:report.csv',
            'cloudomation:report.sig',
            # attach files from an URL
            'https://cloudomation.com/wp-content/uploads/2020/11/1-1.jpg'
        ],
    )
    return this.success('all done')

REST

The REST connector allows to make multipart POST requests with file parts from Engine.

example

Make a multipart POST request containing a file from Engine

import flow_api

def handler(system: flow_api.System, this: flow_api.Execution, inputs: dict):
    this.connect(
        connector_type='REST',
        url='https://httpbingo.org/post',
        method='POST',
        multipart={
            'parts': [
                {
                    'name': 'string-field',
                    'value': 'spam & eggs',
                },
                {
                    'name': 'file',
                    'file': 'report.txt',
                },
            ],
        },
    )
    return this.success('all done')

Learn More

Git Integration

Connector Types