slack-webhook

• Send notifications to a specific channel
• CI/CD notifications, alerts, status updates
• Quick integration without full Slack app setup

```bash

export SLACK_WEBHOOK_URL=https://hooks.slack.com/services/T00000000/B00000000/XXXXXXXX

```

Get Webhook URL

1. Create app: https://api.slack.com/apps → Create New App → From scratch
2. Select Incoming Webhooks → Toggle On
3. Click Add New Webhook to Workspace
4. Select channel → Allow
5. Copy Webhook URL

> Important: When using $VAR in a command that pipes to another command, wrap the command containing $VAR in bash -c '...'. Due to a Claude Code bug, environment variables are silently cleared when pipes are used directly.

> ```bash

> bash -c 'curl -s "https://api.example.com" -H "Authorization: Bearer $API_KEY"' | jq .

> ```

Simple Message

Write to /tmp/slack_request.json:

```json

{

"text": "Hello, world."

}

```

Then run:

```bash

bash -c 'curl -X POST $SLACK_WEBHOOK_URL -H "Content-type: application/json" -d @/tmp/slack_request.json'

```

With Formatting

Write to /tmp/slack_request.json:

```json

{

"text": "Bold and _italic_ text"

}

```

Then run:

```bash

bash -c 'curl -X POST $SLACK_WEBHOOK_URL -H "Content-type: application/json" -d @/tmp/slack_request.json'

```

With Link

Write to /tmp/slack_request.json:

```json

{

"text": "Check "

}

```

Then run:

```bash

bash -c 'curl -X POST $SLACK_WEBHOOK_URL -H "Content-type: application/json" -d @/tmp/slack_request.json'

```

With Blocks (Rich Layout)

Write to /tmp/slack_request.json:

```json

{

"text": "New review submitted",

"blocks": [

{

"type": "section",

"text": {

"type": "mrkdwn",

"text": "Danny left the following review:"

}

},

{

"type": "section",

"text": {

"type": "mrkdwn",

"text": "\n:star:\nDoors had too many axe holes."

}

}

]

}

```

Then run:

```bash

bash -c 'curl -X POST $SLACK_WEBHOOK_URL -H "Content-type: application/json" -d @/tmp/slack_request.json'

```

With Fields

Write to /tmp/slack_request.json:

```json

{

"text": "Deployment status",

"blocks": [

{

"type": "section",

"fields": [

{

"type": "mrkdwn",

"text": "Environment:\nProduction"

},

{

"type": "mrkdwn",

"text": "Status:\nSuccess"

}

]

}

]

}

```

Then run:

```bash

bash -c 'curl -X POST $SLACK_WEBHOOK_URL -H "Content-type: application/json" -d @/tmp/slack_request.json'

```

| Syntax | Result |

|--------|--------|

| bold | bold |

| _italic_ | _italic_ |

| ~strike~ | ~~strike~~ |

| ` code | code` |

| \n | newline |

| | hyperlink |

| :emoji: | emoji |

Messages with ! may fail due to shell history expansion. Use heredoc:

```bash

bash -c 'curl -s -X POST $SLACK_WEBHOOK_URL -H "Content-type: application/json" -d @-' << 'EOF'

{"text":"Deploy completed! :rocket:"}

EOF

```

Success: ok (HTTP 200)

Errors:

• invalid_payload - Malformed JSON
• no_text - Missing text field
• no_service - Webhook disabled or invalid
• channel_not_found - Channel deleted
• channel_is_archived - Channel archived
• action_prohibited - Admin restriction

• One webhook = one channel only
• Cannot override username or icon (set in app config)
• Send only (no reading messages)
• Cannot delete messages after posting
• Rate limit: 1 message/second

For full API access, use the slack skill with Bot Token.

• Webhooks Guide: https://docs.slack.dev/messaging/sending-messages-using-incoming-webhooks
• Block Kit Builder: https://app.slack.com/block-kit-builder
• Message Formatting: https://docs.slack.dev/messaging/formatting-message-text