Literal Line Prefix Filter
Filter hard-line contents by an exact literal prefix; preserve source line numbers and offsets, without regex interpretation.
Description
Filter hard-line contents by an exact literal prefix; preserve source line numbers and offsets, without regex interpretation.
A literal prefix filter finds line contents beginning with a chosen string. It is useful for headers, comment prefixes or simple record markers.
When to use this tool
Filter hard-line contents by an exact literal prefix; preserve source line numbers and offsets, without regex interpretation.
- Prepare the supplied text, affix 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 text, affix. 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.lines. Interpret false, null and empty lists using the distinctions below; they can be valid outputs.
Split recognized newline sequences and test each content with case-sensitive startsWith(affix). Return the one-based line number, text and zero-based UTF-16 start offset of each match.1
| Input field | Meaning and representation | Accepted input |
|---|---|---|
| text | text. | Text; at most 8,192 UTF-16 code units, subject to the grammar above |
| affix | affix. | 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.lines | The lines list in the ordering and representation described above. |
{
"input": {
"text": "ax\nbx\nc",
"affix": "a"
},
"output": {
"result": {
"lines": [
{
"line": 1,
"text": "ax",
"start": 0
}
]
}
}
}Limitations and assumptions
- Prefixes begin at the actual line start, including indentation. Empty prefixes match all lines; there is no case folding, regex interpretation or automatic whitespace removal.
- Text offsets and lengths use UTF-16 code units unless explicitly described as bytes or code points. CRLF, CR and LF are recognized as line endings; a terminal newline creates a final empty line in the shared line model.
- 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.
- Ordinary string lists have at most 128 entries of at most 128 code units each; numeric lists and matrices have separate bounded size checks. 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 parser or language-aware editor when quoting, syntax or nested constructs matter. For plain text transforms, keep UTF-16 offsets, Unicode code points, grapheme clusters and UTF-8 byte offsets distinct; apply changes to the same source version used to calculate spans.
References
Similar or alternative tools
- Literal Line Comment Prefix Toggle
Toggle a literal comment prefix at column zero for all hard lines: remove only when every line has it, otherwise add to all.
- Literal Line Suffix Filter
Filter hard-line contents by an exact literal suffix; preserve source line numbers and offsets, without regex interpretation.