> ## Documentation Index
> Fetch the complete documentation index at: https://instro.nominal.io/llms.txt
> Use this file to discover all available pages before exploring further.

# Publishers: publish JSONL

```python publish_jsonl.py theme={null}
"""Example: Publishers: publish JSONL.

Demonstrates publishing measurements to a newline-delimited JSON file (FilePublisher).

Start the simulated PSU first:
    python -m instro.psu.scpi_sim_server

Then in another shell:
    python examples/publishers/publish_jsonl.py
"""

import time

from instro.lib.publishers import FilePublisher
from instro.psu import InstroPSU
from instro.psu.drivers import SimulatedPSU

VISA_RESOURCE = "TCPIP0::127.0.0.1::5025::SOCKET"

file_publisher = FilePublisher(directory="./captures", format="jsonl", custom_file_name="psu_capture")

psu = InstroPSU(
    name="myPSU",
    driver=SimulatedPSU(VISA_RESOURCE),
    num_channels=2,
    publishers=[file_publisher],
)

with psu:
    psu.set_current_limit(0.2, channel=1)
    psu.output_enable(True, channel=1)

    # Voltage sweep. Every command and measurement is appended to the
    # capture file as one complete JSON line.
    for v in range(5):
        psu.set_voltage(v, channel=1)
        time.sleep(0.5)
        psu.get_voltage(channel=1)
        psu.get_current(channel=1)

    psu.output_enable(False, channel=1)

print(f"Wrote {file_publisher.file_path}:")
print(file_publisher.file_path.read_text(), end="")
```