# Hello, World!
The goal of this tutorial is to build a simple ByteNite app that outputs the string "Hello, World!" to a file. Use this tutorial if you're new to ByteNite and want to have a quick sense of the workflow.
| Duration | Difficulty | Prerequisites |
| -------- | ------------------------------------------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| \~15 min | Very Easy |
|
***
{% stepper %}
{% step %}
### Download sample app
Run the `app new` command in your terminal to create an app directory locally named "hello-world":
```bash
bytenite app new hello-world
```
Check that a new directory named "hello-world" was indeed created at your base path:
```
ls
```
{% endstep %}
{% step %}
### Write the main script
Locate your pre-generated Python entry point (`./hello-world/app/main.py)` and add the code to the file.
We'll make the app perform a few simple steps:
* Read a string from the input text file (chunk).
* Convert the string to a case matching the input parameter 'case'.
* Write the result to a text file in the task results directory.
{% code title="main.py" fullWidth="true" %}
```python
if __name__ == '__main__':
print("Python task started")
result_path = os.path.join(task_results_dir, 'processed_chunk.txt')
try:
# 1. Reading Inputs
# Expect a text file to be passed by the partitioner
with open(chunk_path, 'r', encoding="utf-8") as infile:
my_string = infile.read()
# 2. Handling Parameters
# Expect the job parameters to have a key named 'case', and the options to be "upper", "lower", and "title"
case = app_params['case']
# 3. Developing the Core Functionality
# Process the string based on the case parameter
if case == "upper":
my_string = my_string.upper()
elif case == "lower":
my_string = my_string.lower()
elif case == "title":
my_string = my_string.title()
else:
my_string = my_string
# 4. Saving Outputs
# Save the string directly into a text file to the default task results directory
with open(os.path.join(task_results_dir, "hello_world_processed.txt"), 'w', encoding="utf-8") as outfile:
outfile.write(my_string)
except Exception as e:
print("Python exception: ", e)
raise e
```
{% endcode %}
{% endstep %}
{% step %}
### Check your manifest and template files
The manifest and template files are automatically generated and located in your `hello-world` directory. Ensure they contain the correct configurations as shown below.
Note: We're using passthrough partitioning and assembling engines in this template, so there's no need to configure these components.
{% code title="manifest.json" %}
```json
{
"name": "hello-world",
"version": "0.1",
"platform": "docker",
"description": "An app named hello-world",
"entrypoint": "main.py",
"platform_config": {
"container": "python:latest"
},
"device_requirements": {
"min_cpu": 2,
"min_memory": 2
}
}
```
{% endcode %}
{% code title="template.json" %}
```json
{
"id": "hello-world-template",
"description": "A template for hello-world",
"app": "hello-world",
"partitioner": "passthrough",
"assembler": "passthrough"
}
```
{% endcode %}
{% endstep %}
{% step %}
### Submit and activate your app
Upload the content of your app:
```bash
bytenite app push hello-world
```
Activate your app to make it accept jobs:
```
bytenite app activate hello-world
```
Now, check your app's details and status by running the command:
```
bytenite app get hello-world
```
Finally, ensure that your template was correctly uploaded—you will need that for running jobs.
```
bytenite template get hello-world-template
```
{% endstep %}
{% step %}
### Launch a job with 'hello-world-template'
Let's launch a job with your new `hello-world-template` and test your app.
Send a POST request to the Job [create](https://docs.bytenite.com/api-reference/customer-api/jobs/create "mention") endpoint, including the following fields in the request body:
Then, launch your job and check the results.
Here's a Postman collection that you can use to run your Hello World job:
{% embed url="" %}
{% endstep %}
{% endstepper %}
---
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```
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```
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