Combine Multiple Uploaded Files into a Single File

Merges a list of locally stored files (from a Shiny fileInput with multiple = TRUE) into a single temporary file, ready for downstream processing such as sending to an LLM. Supports PDF (merged page-by-page) and plain text types including .txt, .mod, .ctl, and .cpp (concatenated). On error, a Shiny notification is shown to the user and NULL is returned rather than stopping the session.

Usage

combine_uploaded_files(file_paths, file_names)

Arguments

file_paths

Character vector of temporary file paths, drawn from input$<inputId>$datapath after a Shiny fileInput upload.

file_names

Character vector of original file names, drawn from input$<inputId>$name. Used to determine file type via extension, since browser-reported MIME types are unreliable for types such as .mod and .ctl.

Value

A length-one character string: the path to a temporary file containing the combined content, or NULL if an error occurred (in which case a Shiny notification is shown). The file lives in tempdir() and will be cleaned up at the end of the R session.

Details

File type is determined from the extension of file_names rather than the browser-reported MIME type, as browsers often report generic "application/octet-stream" for domain-specific extensions such as .ctl and .mod.

This function assumes all files share the same extension. If they do not, a Shiny error notification is shown and NULL is returned. It is expected that this validation is performed by the caller (see the Shiny server example) before calling this function.

Combination strategy by extension:

.pdf

Pages are merged in order using pdf_combine. Requires the pdftools package.

.txt, .mod, .ctl

Files are read with readLines and concatenated with a newline separator. Output is written as .txt.

All other extensions

A Shiny error notification is shown and NULL is returned.

See also

fileInput for the UI element that produces the input, showNotification for the notification system, pdf_combine for the underlying PDF merge.

Examples

if (FALSE) { # \dontrun{
# Inside a Shiny server function:
observe({
  req(input$pdffile_model_1)
  files <- input$pdffile_model_1

  combined_path <- if (nrow(files) > 1) {
    combine_uploaded_files(files$datapath, files$name)
  } else {
    files$datapath[1]
  }

  req(!is.null(combined_path))
  send_to_llm(combined_path)
})
} # }