read: Unified file reading block

In blockr.io: Interactive File Import and Export Blocks

Unified file reading block

Description

A single block for reading files in various formats with smart UI that adapts based on detected file type. Supports "From Browser" (upload) and "From Server" (browse) modes with persistent storage for uploaded files.

Usage

new_read_block(
  path = character(),
  source = "upload",
  combine = "auto",
  args = list(),
  ...
)

Arguments

path	Character vector of file paths to pre-load. When provided, automatically switches to "path" mode regardless of the source parameter.
source	Either "upload" for file upload widget, "path" for file browser, or "url" for URL download. Default: "upload". Automatically set based on path parameter.
combine	Strategy for combining multiple files: "auto", "rbind", "cbind", "first"
args	Named list of format-specific reading parameters. Only specify values that differ from defaults. Available parameters: For CSV files: sep (default: ","), quote (default: '"'), encoding (default: "UTF-8"), skip (default: 0), n_max (default: Inf), col_names (default: TRUE) For Excel files: sheet (default: NULL), range (default: NULL), skip (default: 0), n_max (default: Inf), col_names (default: TRUE)
...	Forwarded to blockr.core::new_data_block()

Details

File Handling Modes

The block supports three modes:

From Browser mode (upload):

• User uploads files from their computer via the browser

• Files are copied to persistent storage directory (upload_path)

• State stores permanent file paths

• Works across R sessions with state restoration

From Server mode (path):

• User picks files that already exist on the server

• No file copying, reads directly from original location

• State stores selected file paths

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

URL mode:

• User provides a URL to a data file

• File is downloaded to temporary location each time

• Always fetches fresh data from URL

• State stores the URL (not file path)

Smart Adaptive UI

After file selection, the UI detects file type and shows relevant options:

• CSV/TSV: Delimiter, quote character, encoding options

• Excel: Sheet selection, cell range

• Other formats: Minimal or no options (handled automatically)

Multi-file Support

When multiple files are selected:

• "auto": Attempts rbind, falls back to first file if incompatible

• "rbind": Row-binds files (requires same columns)

• "cbind": Column-binds files (requires same row count)

• "first": Uses only the first file

Value

A blockr data block that reads file(s) and returns a data.frame.

Configuration

The following settings are retrieved from options and not stored in block state:

• volumes: File browser mount points. Set via options(blockr.volumes = c(name = "path")) or environment variable BLOCKR_VOLUMES. Default: c(temp = tempdir())

• upload_path: Directory for persistent file storage. Set via options(blockr.upload_path = "/path") or environment variable BLOCKR_UPLOAD_PATH. Default: rappdirs::user_data_dir("blockr")

Examples

# Create a read block for a CSV file
csv_file <- tempfile(fileext = ".csv")
write.csv(mtcars[1:5, ], csv_file, row.names = FALSE)
block <- new_read_block(path = csv_file)
block

# With custom CSV parameters
block <- new_read_block(
  path = csv_file,
  args = list(n_max = 3)
)

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

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