---
title: Arguments (positional)
description: Mark a parameter with [Argument] to make it positional. Indices must start at 0 and be consecutive. Combine [Argument] with a T[] type (or params T[])...
url: https://docs-v3-preview.elastic.dev/argh/parameters/arguments
---

# Arguments (positional)
Mark a parameter with `[Argument]` to make it positional. Indices must start at `0` and be consecutive.
```csharp
public static Task<int> Deploy([Argument] string environment) { … }
// myapp deploy production
```


## Variadic positionals

Combine `[Argument]` with a `T[]` type (or `params T[]`) to collect all remaining tokens into an array. The variadic argument must be the last positional. Zero items is valid.
Because C# requires `params` to be the last method parameter, a variadic positional can appear after flags in the method signature.
```csharp
public static void Copy([Argument] string dest, [Argument] params string[] files) { … }
// myapp copy ./out/ a.txt b.txt "path with spaces/c.txt"
```

Flags can appear before or after variadic tokens on the command line:
```csharp
public static void Archive([Argument] params string[] files, bool verbose = false) { … }
// myapp archive a.zip b.zip --verbose
```

Mixed scalar positional, flags, and variadic arguments work together. Note that `params` must be the last C# parameter:
```csharp
public static void Tag([Argument] string target, bool force, [Argument] params string[] tags) { … }
// myapp tag main-branch --force tag1 tag2 tag3
```


## Help output

Variadic positionals appear as `<files...>` / `[<files...>]` in `--help` and include a `[variadic]` annotation.

## Count validation

Apply `[MinLength(n)]` or `[MaxLength(n)]` to validate the item count:
```csharp
public static void Archive([Argument][MinLength(1)][MaxLength(20)] string[] files) { … }
// --help: <files...>   [variadic] [count: 1–20]
```


## Ordering rules

<important>
  - All `[Argument]` positionals must precede flags in the parameter list (by convention).
  - Variadic positionals must be the last positional.
  - `params` must be the last method parameter (C# requirement).
  - Flags can appear before or after positional tokens on the actual command line.
</important>