fill

Fills empty or null values with specified values or strategies (forward-fill, backward-fill).

Write with --output. A trailing path is not a positional argument.

# Fill with constant value
undatum fill data.csv --fields name,email --value "N/A" --output output.csv

# Forward fill (use previous value)
undatum fill data.jsonl --fields status --strategy forward --output output.jsonl

# Backward fill (use next value)
undatum fill data.csv --fields category --strategy backward --output output.csv

Key options: --fields, --value, --strategy forward|backward, --output. Also accepts --table, --flatten-nested, --on-error, --error-log, and --quotechar (shared options).