dtset — Excel Cell Writer (alpha)

Modify cells in existing .xlsx/.xlsm files. Preserves formatting, formulas, and all structure it doesn't touch. Saves atomically, so a failed write never corrupts the original.

Only .xlsx and .xlsm. Other formats (CSV, Parquet, JSON, .xls, .ods) are rejected with exit code 2; there is no dt tool that edits them in place.

Alpha build. dtset is not in the dt-cli-tools release binaries. If command -v dtset finds nothing, install it from a dt-cli-tools checkout: cargo install --path . --features alpha.

Quick Reference

# Set a single cell
dtset file.xlsx A1=42

# Set multiple cells
dtset file.xlsx A1=42 B2="hello world" C3=true

# Force type with tag (e.g., preserve leading zero)
dtset file.xlsx A1:str=07401

# Target a specific sheet (name or 0-based index)
dtset file.xlsx --sheet Revenue A1=42

# Write to a new file (don't modify original)
dtset file.xlsx -o new.xlsx A1=42

# Bulk update from CSV
dtset file.xlsx --from updates.csv

# Bulk from stdin
echo "A1,42" | dtset file.xlsx --from -

Type Inference

Values are auto-detected:

• 42 → integer, 3.5 → float
• true/false → boolean
• 2024-01-15 → date
• Everything else → string

Override with tags: :str, :num, :bool, :date

CSV Format

cell,value
A1,42
B2,hello
C3:str,07401

The header row is optional. Standard RFC 4180 quoting for values with commas: A1,"hello, world"

Exit Codes

Workflow

1. Use dtcat file.xlsx first to see current content (--sheet for other sheets)
2. Use dtset to modify cells
3. Use dtcat again to verify changes