Progress bar in the terminal

Description

Progress bars are configurable, may include percentage, elapsed time, and/or the estimated completion time. They work in the command line, in Emacs and in R Studio. The progress package was heavily influenced by https://github.com/tj/node-progress

Creating the progress bar

A progress bar is an R6 object, that can be created with progress_bar$new(). It has the following arguments:

format

The format of the progress bar. A number of tokens can be used here, see them below. It defaults to "[:bar] :percent", which means that the progress bar is within brackets on the left, and the percentage is printed on the right.

total

Total number of ticks to complete. Defaults to 100.

width

Width of the progress bar. Default is the current terminal width (see options() and width) minus two.

stream

The output stream to put the progress bar on. It defaults to stderr(), except in R Studio that has a bug when printing on the standard error, so there we use stdout. If the output stream is not a terminal and we are not in R Studio, then no progress bar is printed.

complete

Completion character, defaults to =.

incomplete

Incomplete character, defaults to -.

callback

Callback function to call when the progress bar finishes. The progress bar object itself is passed to it as the single parameter.

clear

Whether to clear the progress bar on completion. Defaults to TRUE.

show_after

Amount of time in seconds, after which the progress bar is shown on the screen. For very short processes, it is probably not worth showing it at all. Defaults to two tenth of a second.

force

Whether to force showing the progress bar, even if the given (or default) stream does not seem support it.

Using the progress bar

Two functions can update a progress bar. progress_bar$tick() increases the number of ticks by one (or another specified value). progress_bar$update() sets a given ratio.

The progress bar is displayed after the first 'tick' command. This might not be desirable for long computations, because nothing is shown before the first tick. It is good practice to call 'tick(0)' at the beginning of the computation or download, which shows the progress bar immediately.

Tokens

They can be used in the format argument when creating the progress bar.

:bar

The progress bar itself.

:current

Current tick number.

:total

Total ticks.

:elapsed

Elapsed time in seconds.

:eta

Estimated completion time in seconds.

:percent

Completion percentage.

:rate

Download rate, bytes per second. See example below.

:bytes

Shows :current, formatted as bytes. Useful for downloads or file reads if you don't know the size of the file in advance. See example below.

:spin

Shows a spinner that updates even when progress is advanced by zero.

Custom tokens are also supported, and you need to pass their values to progress_bar$tick() or progress_bar$update(), in a named list. See example below.

Examples

## We don't run the examples on CRAN, because they takes >10s
## altogether. Unfortunately it is hard to create a set of
## meaningful progress bar examples that also run quickly.
## Not run: 

## Basic
pb <- progress_bar$new(total = 100)
for (i in 1:100) {
  pb$tick()
  Sys.sleep(1 / 100)
}

## ETA
pb <- progress_bar$new(
  format = "  downloading [:bar] :percent eta: :eta",
  total = 100, clear = FALSE, width= 60)
for (i in 1:100) {
  pb$tick()
  Sys.sleep(1 / 100)
}

## Elapsed time
pb <- progress_bar$new(
  format = "  downloading [:bar] :percent in :elapsed",
  total = 100, clear = FALSE, width= 60)
for (i in 1:100) {
  pb$tick()
  Sys.sleep(1 / 100)
}

## Spinner
pb <- progress_bar$new(
  format = "(:spin) [:bar] :percent",
  total = 30, clear = FALSE, width = 60)
for (i in 1:30) {
  pb$tick()
  Sys.sleep(3 / 100)
}

## Custom tokens
pb <- progress_bar$new(
  format = "  downloading :what [:bar] :percent eta: :eta",
  clear = FALSE, total = 200, width = 60)
f <- function() {
  for (i in 1:100) {
    pb$tick(tokens = list(what = "foo   "))
    Sys.sleep(2 / 100)
  }
  for (i in 1:100) {
    pb$tick(tokens = list(what = "foobar"))
    Sys.sleep(2 / 100)
  }
}
f()

## Download (or other) rates
pb <- progress_bar$new(
  format = "  downloading foobar at :rate, got :bytes in :elapsed",
  clear = FALSE, total = 1e7, width = 60)
f <- function() {
  for (i in 1:100) {
    pb$tick(sample(1:100 * 1000, 1))
    Sys.sleep(2/100)
  }
  pb$tick(1e7)
  invisible()
}
f()


## End(Not run)