write: Unified file writing block

In blockr.io: Interactive File Import and Export Blocks

Unified file writing block

Description

A variadic block for writing dataframes to files in various formats. Accepts multiple input dataframes and handles single files, multi-sheet Excel, or ZIP archives depending on format and number of inputs.

Usage

new_write_block(
  directory = "",
  filename = "",
  format = "csv",
  mode = "download",
  auto_write = FALSE,
  args = list(),
  ...
)

Arguments

directory	Character. Default directory for file output (browse mode only). Can be configured via options(blockr.write_dir = "/path") or environment variable BLOCKR_WRITE_DIR. Default: tempdir().
filename	Character. Optional fixed filename (without extension). If provided: Writes to same file path on every upstream change (auto-overwrite) If empty (default): Generates timestamped filename (e.g., data_20250127_143022.csv)
format	Character. Output format: "csv", "excel", "parquet", or "feather". Default: "csv"
mode	Character. Either "download" for "To Browser" (triggers browser download), or "browse" for "To Server" (writes to server filesystem). Default: "download"
auto_write	Logical. When TRUE, automatically writes files when data changes (browse mode only). When FALSE (default), user must click "Submit" button to save. Has no effect in download mode.
args	Named list of format-specific writing parameters. Only specify values that differ from defaults. Available parameters: For CSV files: sep (default: ","), quote (default: TRUE), na (default: "") For Excel/Arrow: Minimal options needed (handled by underlying packages)
...	Forwarded to blockr.core::new_transform_block()

Details

Variadic Inputs

This block accepts multiple dataframe inputs (1 or more) similar to bind_rows_block. Inputs can be numbered ("1", "2", "3") or named ("sales_data", "inventory"). Input names are used for sheet names (Excel) or filenames (multi-file ZIP).

File Output Behavior

Single input:

• Writes single file in specified format

• Filename: ⁠{filename}.{ext}⁠ or ⁠data_{timestamp}.{ext}⁠

Multiple inputs + Excel:

• Single Excel file with multiple sheets

• Sheet names derived from input names

Multiple inputs + CSV/Arrow:

• Single ZIP file containing individual files

• Each file named from input names

Filename Behavior

Fixed filename (filename = "output"):

• Reproducible path: always writes to ⁠{directory}/output.{ext}⁠

• Overwrites file on every upstream data change

• Ideal for automated pipelines

Auto-timestamped (filename = ""):

• Unique files: ⁠{directory}/data_YYYYMMDD_HHMMSS.{ext}⁠

• Preserves history, prevents accidental overwrites

• Safe default behavior

Mode: To Browser vs To Server

To Browser mode (download):

• Exports files to your computer

• Triggers a download to your browser's download folder

• Useful for exporting results

To Server mode (browse):

• Saves files directly on the server

• User selects directory with file browser

• Files persist on server

• When running locally, this is your computer's file system

Value

A blockr transform block that writes dataframes to files

Examples

# Create a write block for CSV output
block <- new_write_block(
  directory = tempdir(),
  filename = "output",
  format = "csv"
)
block

# Write block for Excel with auto-timestamp
block <- new_write_block(
  directory = tempdir(),
  filename = "",
  format = "excel"
)

if (interactive()) {
  # Launch interactive app
  serve(new_write_block())
}

blockr.io documentation built on Jan. 7, 2026, 9:06 a.m.