fmt

Reformats tabular data as CSV with an explicit dialect (delimiter, quote style, escape character, line endings).

# Change delimiter
undatum fmt data.csv --delimiter ";" --output output.csv

# Change quote style
undatum fmt data.csv --quote always --output output.csv

# Change escape character
undatum fmt data.csv --escape backslash --output output.csv

# Change line endings
undatum fmt data.csv --line-ending crlf --output output.csv

Without --output, CSV is written to stdout.

Options

Flag	Values	Default
--delimiter	Any single character	,
--quote	minimal, always, none, nonnumeric	minimal
--escape	double, backslash, none	double
--line-ending	unix, windows, crlf, mac	unix
--quotechar	CSV quote character	iterabledata default "
--encoding	Text encoding	utf8
--output	Output path	stdout

Also accepts --table, --flatten-nested, --on-error, and --error-log (shared options).

Reference

Reads: CSV and TSV · Writes: CSV with the chosen dialect · Memory: streaming, two passes over the input · Engines: python

undatum fmt [OPTIONS] INPUT_FILE

Argument	Description
INPUT_FILE	Path to input file. (required)

Option	Description	Default
-o, --output TEXT	Optional output file path. If not specified, prints to stdout.
-d, --delimiter TEXT	CSV delimiter character (default: comma).	,
--quotechar TEXT	CSV quote character (iterabledata default '"' when omitted).
--quote TEXT	Quote style: 'minimal' (default), 'always', 'none', or 'nonnumeric'.	minimal
--escape TEXT	Escape character: 'double' (default), 'backslash', or 'none'.	double
--line-ending TEXT	Line ending: 'unix' (default), 'windows', 'crlf', or 'mac'.	unix
--encoding TEXT	File encoding (e.g., 'utf8', 'latin1').
--verbose / --no-verbose	Enable verbose logging output.	--no-verbose
-F, --format-in TEXT	Override input file format detection (e.g., 'csv', 'jsonl').
--table, --sheet TEXT	Table or sheet name for multi-table sources (Excel, SQLite, lakehouse).
--start-page INTEGER	Sheet index (0-based) for Excel files.	0
--trust	Acknowledge pickle deserialization risk when reading pickle sources.
--on-error TEXT	Parse-error policy: raise (default), skip, or warn.
--error-log TEXT	Append parse errors as JSONL (use with --on-error skip or warn).
--flatten-nested	Unfold nested dict / array-of-dict fields into dotted paths (e.g. city.lat).
--max-nested-depth INTEGER	With --flatten-nested, maximum nest depth to unfold (engine default 5).
--keep-nested-parents / --no-keep-nested-parents	With --flatten-nested, keep parent dict/array fields alongside dotted children.	--keep-nested-parents

See also shared options.