Convert File by @duckdb

You are helping the user convert a data file from one format to another using DuckDB.

Input file: $0 Output file: ${1:-}

Step 1 — Resolve input and output

Input: $0. If it's a bare filename (no /), resolve to a full path with find "$PWD" -name "$0" -not -path '*/.git/*' 2>/dev/null | head -1.

Output: If $1 is provided, use it as the output path. If not, default to the same stem as the input with a .parquet extension (e.g., data.csv → data.parquet).

Infer the output format from the output file extension:

Extension	Format clause
`.parquet`, `.pq`	(default, no clause needed)
`.csv`	`(FORMAT csv, HEADER)`
`.tsv`	`(FORMAT csv, HEADER, DELIMITER '\t')`
`.json`	`(FORMAT json, ARRAY true)`
`.jsonl`, `.ndjson`	`(FORMAT json, ARRAY false)`
`.xlsx`	`(FORMAT xlsx)` — requires `INSTALL excel; LOAD excel;`
`.geojson`	`(FORMAT GDAL, DRIVER 'GeoJSON')` — requires `LOAD spatial;`
`.gpkg`	`(FORMAT GDAL, DRIVER 'GPKG')` — requires `LOAD spatial;`
`.shp`	`(FORMAT GDAL, DRIVER 'ESRI Shapefile')` — requires `LOAD spatial;`

Step 2 — Convert

Run a single DuckDB command. Prepend extension loads as needed based on both the input and output formats.

duckdb -c "
<EXTENSION_LOADS>
COPY (FROM '<INPUT_PATH>') TO '<OUTPUT_PATH>' <FORMAT_CLAUSE>;
"

For remote inputs (s3://, https://, etc.), prepend the same protocol setup as read-file:

Protocol	Prepend
`s3://`	`LOAD httpfs; CREATE SECRET (TYPE S3, PROVIDER credential_chain);`
`gs://` / `gcs://`	`LOAD httpfs; CREATE SECRET (TYPE GCS, PROVIDER credential_chain);`
`https://` / `http://`	`LOAD httpfs;`

If the user mentions partitioning (e.g., "partition by year"), add PARTITION_BY (col) to the format clause. This only works with Parquet and CSV output.

If the user mentions compression (e.g., "use zstd"), add CODEC 'zstd' for Parquet output.

Step 3 — Report

On success, report:

Input file and detected format
Output file, format, and size (ls -lh)
Row count if quick to compute

On failure:

duckdb: command not found → delegate to /duckdb-skills:install-duckdb
Missing extension → install it and retry
Input parse error → suggest the user check the input format or try /duckdb-skills:read-file first to inspect it