Lesath

Strict XLSX and ODS spreadsheet interchange for Ruby

Features · Installation · Quick start · Limits · Development

Lesath reads and writes a documented subset of .xlsx and .ods workbooks. It preserves supported cell content and rejects unsupported features instead of silently dropping them. It is a library for spreadsheet interchange, not a spreadsheet UI or calculation engine. The name comes from Lesath (υ Scorpii), from Arabic lasʿa, “sting.”

• Read and write XLSX and ODS with multiple ordered sheets and sparse cells.
• Store strings, finite numbers, booleans, and same-format formula text with a cached scalar value.
• Reject unsupported package parts, XML content, and spreadsheet features on import; refuse to overwrite an existing file on export.

Requires CRuby 3.2 or newer:

gem install lesath

require "lesath"

book = Lesath::Workbook.new
book.add_sheet("Sales")
book.set("Sales", 1, 1, "Item")
book.set("Sales", 2, 1, "Tea")
book.set("Sales", 2, 2, 12.5)

Lesath.write(book, "sales.xlsx")
copy = Lesath.read("sales.xlsx")
copy.cell("Sales", 2, 2).value # => 12.5

Cell coordinates are one-based. Lesath.read and Lesath.write infer the format from .xlsx or .ods; use format: :xlsx or format: :ods to select it explicitly. Lesath.write raises an error if the target already exists.

Lesath supports up to 200 sheets, 100,000 populated cells, 1,048,576 rows, 16,384 columns, 15-digit integers, 32,767 UTF-16 units per string, and 31 characters per sheet name. XLSX uses inline strings and simple scalar cached formulas. ODS supports unstyled scalar cells and repeated blank rows and cells. Both formats retain sheet order and names.

Formula text and its cached value are stored, but never evaluated. XLSX formulas begin with =, ODS formulas with of:=. Formula cells require a cached value, and Lesath rejects formula export to the other format: it does not translate formula languages. Callers must update cached values after formula inputs change. Without formulas, supported cells can be written to either format.

Styles, rich text, dates and times, merged cells, comments, charts, images, macros, validations, hyperlinks, named ranges, external links, and other unsupported package parts or XML elements are rejected on import with Lesath::UnsupportedFeature. ODS strings that need <text:s>, tabs, or line breaks are also rejected instead of changing their display text. Invalid ZIP packages, size limits, and XML DTDs raise Lesath::InvalidPackage. Generated files are checked against the same ZIP limits before creating the target path. This strict subset does not promise round trips for general Excel or LibreOffice files.

Rukbat::Workbook is not directly accepted: its formatting and formula semantics need an explicit adapter and loss policy. Until then, CSV remains the broader interchange path. See ADR 001 for the exact boundary and source standards.

bundle install
bundle exec rake spec
gem build --strict lesath.gemspec

Lesath is released under the MIT License.