Leading Dot Filename Extension Split
Split the final filename extension while preserving a leading-dot-only name as extensionless; a trailing dot gives an empty extension.
Description
Split the final filename extension while preserving a leading-dot-only name as extensionless; a trailing dot gives an empty extension.
A leading dot alone does not count as a filename extension under this final-dot policy.
When to use this tool
Split the final filename extension while preserving a leading-dot-only name as extensionless; a trailing dot gives an empty extension.
- Prepare the supplied name fields for this operation.
- Compare the complete example with the representation used by your own input before carrying the result into another step.
How to use the tool and how it works
- Enter name. Use the exact text syntax, units and index conventions explained below.
- Run the tool. If input validation fails, correct the supplied fields before interpreting any result.
- Read result.stem, result.extension. Interpret false, null and empty lists using the distinctions below; they can be valid outputs.
Validate a single non-dot POSIX filename. Split at the last dot only when its index is greater than zero, otherwise return the whole stem and extension null.1
| Input field | Meaning and representation | Accepted input |
|---|---|---|
| name | name. | Text; at most 8,192 UTF-16 code units, subject to the grammar above |
| Output field | Interpretation |
|---|---|
| result | Object containing the named outputs below. |
| result.stem | The stem value under the stated formula or text convention. |
| result.extension | Nullable extension; the condition for absence is described above. |
{
"input": {
"name": ".config"
},
"output": {
"result": {
"stem": ".config",
"extension": null
}
}
}Limitations and assumptions
- A trailing eligible dot yields an empty extension string. No multi-extension semantic or file-type inference is applied.
- Every declared top-level field is required and unexpected fields are rejected. Numeric inputs must be finite; ordinary text fields are bounded to 8,192 UTF-16 code units, with tighter operation-specific limits where stated.
- String lists have at most 128 entries of at most 128 code units; matrices have at most 128 rows and columns. Larger numeric lists and parsed JSON have separate bounded budgets. Nonfinite results and excessively large serialized outputs are rejected.
- Indexes are zero-based and spans have an exclusive end unless explicitly stated otherwise. A valid false, null or empty-list result is distinct from malformed input.
Alternative or Complementary methods
Use a filesystem-aware implementation with appropriate platform semantics for actual file operations. Literal slash components, Unicode comparison and filename plans do not resolve symlinks or atomically reserve a destination.
References
Similar or alternative tools
- Filename Extension Chain Splitter
Split a filename into stem and all literal extension-chain segments after its first nonleading dot; no MIME inference.
- Filename Extension Chain Replacer
Replace the complete literal extension chain while preserving the leading-dot-aware stem; an empty extension list removes the chain.