Logging provides developers with visibility into process outputs within sandboxes. You can retrieve logs either in batch or streaming.
Complete code examples demonstrating all operations are available on Blaxel’s GitHub: in TypeScript and in Python.

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In batch

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Retrieve from the execution object

Logs for a process are available in the process execution object if the process is started with the waitForCompletion: true / "wait_for_completion": True parameter. Both standard output (stdout) and standard error (stderr) are surfaced: 
import { SandboxInstance } from "@blaxel/core";

const sandbox = await SandboxInstance.get("my-sandbox");

const process = await sandbox.process.exec({
  name: "hello-process",
  command: "echo 'Hello, World!'",
  waitForCompletion: true
});
console.log(process.logs);

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Retrieve from a completed process name or ID

Retrieve logs for a specific process (using either its name or process ID) after it has completed execution. By default, this retrieves standard output (stdout) only: 
const process = await sandbox.process.exec({
  name: "hello-process",
  command: "echo 'Hello, World!'"
});

const logs = await sandbox.process.logs("hello-process");
To retrieve standard error (stderr): 
const errorLogs = await sandbox.process.logs("hello-process", "stderr");
To retrieve both stderr and stdout: 
const allLogs = await sandbox.process.logs("hello-process", "all");

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Streaming

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Retrieve via a callback function

The callback handlers receive log entries in real-time as they’re generated by the process:
  • onLog/on_log: Receives complete log objects with additional metadata
This approach is ideal for long-running processes where you need to monitor progress or respond to specific log events during execution. 
await sandbox.process.exec({
  name: "streaming-demo",
  command: "echo 'Starting process'; sleep 2; echo 'Processing...'; sleep 2; echo 'Completed!
  onLog: (log) => {
    console.log(`LOG: ${JSON.stringify(log)}`);
  }
});

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Retrieve from a process name or ID

Stream logs for a specific process (using either its name or process ID): 
// Start a long-running process
await sandbox.process.exec({
  name: "stream-demo",
  command: "sh -c 'for i in $(seq 1 5); do echo \"Output $i\"; sleep 1; done'"
});

const stream = sandbox.process.streamLogs("stream-demo", {
  onLog: (log) => console.log("Log:", log),
  onStdout: (stdout) => console.log("Stdout:", stdout),
  onStderr: (stderr) => console.log("Stderr:", stderr)
});

// Wait for completion and cleanup
await sandbox.process.wait("stream-demo");
stream.close();