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Unified file writing block

write.Rd

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 = TRUE,
  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: current working directory.

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" to trigger browser download (recommended for beginners), or "browse" to write files to server filesystem. Default: "download"

auto_write

Logical. When TRUE (default), automatically writes files when data changes (browse mode only). When FALSE, user must click "Write File" 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()

Value

A blockr transform block that writes dataframes to files

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: Browse vs Download

Browse mode:

  • Writes files to server filesystem

  • User selects directory with file browser

  • Files persist on server

Download mode:

  • Generates file and triggers browser download

  • File saved to user's download folder

  • Useful for exporting results

Examples

if (FALSE) { # \dontrun{
# Single dataframe to CSV
serve(new_write_block(
  directory = "/tmp",
  filename = "output",
  format = "csv"
))

# Multiple dataframes to Excel with auto-timestamp
serve(new_write_block(
  directory = "/tmp",
  filename = "", # auto-generated
  format = "excel"
))

# CSV with custom delimiter
serve(new_write_block(
  directory = "/tmp",
  filename = "data",
  format = "csv",
  args = list(sep = ";")
))
} # }