---
title: "__P"
description: "JMeter __P function reference: syntax, parameters, and practical examples for parameterizing test plans with dynamic values."
url: https://docs.jmeter.ai/functions/p/
lastUpdated: 2026-10-01
source: docs.jmeter.ai
---

# __P

*Also documented in context in the [full Functions and Variables reference](/user-manual/functions/#__P).*

**TL;DR:** `__P` is the short form of [__property](/functions/property/) built specifically for command-line overrides (`jmeter -Jgroup1.threads=7`) — no variable-saving option, and its implicit default is `1` (chosen to be a safe fallback for thread counts, loops, and ramp-up).

This is a simplified property function which is
intended for use with properties defined on the command line.
Unlike the `__property` function, there is no option to save the value in a variable,
and if no default value is supplied, it is assumed to be 1.
The value of 1 was chosen because it is valid for common test variables such
as loops, thread count, ramp up etc.

For example:
`
Define the property value:

```plaintext
jmeter -Jgroup1.threads=7 -Jhostname1=www.realhost.edu
```

Fetch the values:

`\${__P(group1.threads)}` - return the value of `group1.threads`

`\${__P(group1.loops)}` - return the value of `group1.loops`

`\${__P(hostname,www.dummy.org)}` - return value of property `hostname` or `www.dummy.org` if not defined

`In the examples above, the first function call would return`7`, the second would return `1`and the last would return`[www.dummy.org`](http://www.dummy.org%60)
(unless those properties were defined elsewhere!)

| Name | Required | Description |
| --- | --- | --- |
| Property Name | Yes | The property name to be retrieved. |
| Default Value | No | The default value for the property.             If omitted, the default is set to “`1`”. |

### Example

```bash
jmeter -Jgroup1.threads=7 -Jhostname1=www.example.com
```

```plaintext
${__P(group1.threads)}              → 7
${__P(group1.loops)}                → 1 (undefined property, implicit default)
${__P(hostname,www.dummy.org)}      → www.dummy.org (undefined, explicit default)
```

This is the standard pattern behind CI/CD load tests that tune concurrency per environment without editing the `.jmx` file — see the [CLI Command Builder](/tools/cli-builder/) to construct the `-J` flags.

## Related

- [Functions and Variables Guide](/topics/functions-and-variables/)
- [Regex Extractor Builder](/tools/regex-tester/)
- [Properties Reference](/user-manual/properties-reference/)
- [CLI Command Builder](/tools/cli-builder/)
- [Full Functions Reference](/user-manual/functions/)
- [Component Reference](/user-manual/component-reference/)