# Document Manipulation

    knitr::opts_chunk$set(eval = FALSE)

The `rstudioapi` package provides a small family of functions that can be used to interact with documents open in an RStudio session. For example, the following code could be used to insert a ‘last modified’ comment at the start of a document:

    # construct the text to be inserted
    fmt <- "# This document was last modified on %s.\n"
    text <- sprintf(fmt, Sys.Date())

    # specify a range where this text should be inserted; here,
    # we use the first line; that is, the 'range' between the start
    # of the first row, and the start of the second row
    range <- rstudioapi::document_range(c(1, 0), c(2, 0))
    rstudioapi::insertText(range, text)

By default, these APIs target the editor instance either currently focused by the user, or when no such editor is currently focused, the last focused editor. If you need to target a specific editor instance (for example, you want to write code that inserts text into the console), you can use `getConsoleEditorContext()` to get the `id` for the console editor:

    # get console editor id
    context <- rstudioapi::getConsoleEditorContext()
    id <- context$id

    # send some R code to the console
    rstudioapi::insertText(text = "print(1 + 1)", id = id)

    # see also: `getActiveEditorContext()`, `getSourceEditorContext()`

You can also modify the cursor position through the use of the `setCursorPosition()` and `setSelectionRanges()` APIs.

    # put the cursor at the end of the document -- note that here,
    # `Inf` is automatically truncated to the actual length of the
    # document
    rstudioapi::setCursorPosition(Inf)

    # select the first 10 even lines in the document
    ranges <- lapply(seq(2, by = 2, length.out = 10), function(start) {
      rstudioapi::document_range(
        c(start, 0),
        c(start, Inf)
      )
    })
    rstudioapi::setSelectionRanges(ranges)

See the `?"rstudio-documents"` help page for more details.