Colored terminal output

Description

With crayon it is easy to add color to terminal output, create styles for notes, warnings, errors; and combine styles.

Usage

## Simple styles
red(...)
bold(...)
# ...

## See more styling below

Arguments

Details

ANSI color support is automatically detected and used. Crayon was largely inspired by chalk https://github.com/chalk/chalk.

Crayon defines several styles, that can be combined. Each style in the list has a corresponding function with the same name.

Genaral styles

• reset

• bold

• blurred (usually called ‘dim’, renamed to avoid name clash)

• italic (not widely supported)

• underline

• inverse

• hidden

• strikethrough (not widely supported)

Text colors

• black

• red

• green

• yellow

• blue

• magenta

• cyan

• white

• silver (usually called ‘gray’, renamed to avoid name clash)

Background colors

• bgBlack

• bgRed

• bgGreen

• bgYellow

• bgBlue

• bgMagenta

• bgCyan

• bgWhite

Styling

The styling functions take any number of character vectors as arguments, and they concatenate and style them:

  library(crayon)
  cat(blue("Hello", "world!\n"))

Crayon defines the %+% string concatenation operator, to make it easy to assemble stings with different styles.

  cat("... to highlight the " %+% red("search term") %+%
      " in a block of text\n")

Styles can be combined using the $ operator:

  cat(yellow$bgMagenta$bold('Hello world!\n'))

See also combine_styles().

Styles can also be nested, and then inner style takes precedence:

  cat(green(
    'I am a green line ' %+%
    blue$underline$bold('with a blue substring') %+%
    ' that becomes green again!\n'
  ))

It is easy to define your own themes:

  error <- red $ bold
  warn <- magenta $ underline
  note <- cyan
  cat(error("Error: subscript out of bounds!\n"))
  cat(warn("Warning: shorter argument was recycled.\n"))
  cat(note("Note: no such directory.\n"))

Author(s)

Maintainer: Gábor Csárdi csardi.gabor@gmail.com

Other contributors:

• Brodie Gaslam brodie.gaslam@yahoo.com [contributor]

• Posit Software, PBC [copyright holder, funder]

See Also

Useful links:

• https://r-lib.github.io/crayon/

• https://github.com/r-lib/crayon

• Report bugs at https://github.com/r-lib/crayon/issues

make_style() for using the 256 ANSI colors.

Examples

cat(blue("Hello", "world!"))

cat("... to highlight the " %+% red("search term") %+%
    " in a block of text")

cat(yellow$bgMagenta$bold('Hello world!'))

cat(green(
 'I am a green line ' %+%
 blue$underline$bold('with a blue substring') %+%
 ' that becomes green again!'
))

error <- red $ bold
warn <- magenta $ underline
note <- cyan
cat(error("Error: subscript out of bounds!\n"))
cat(warn("Warning: shorter argument was recycled.\n"))
cat(note("Note: no such directory.\n"))

Convert to character

Description

This function just calls as.character(), but it is easier to type and read.

Usage

chr(x, ...)

Arguments

Value

Character value.

Align an ANSI colored string

Description

Align an ANSI colored string

Usage

col_align(
  text,
  width = getOption("width"),
  align = c("left", "center", "right"),
  type = "width"
)

Arguments

Value

The aligned character vector.

See Also

Other ANSI string operations: col_nchar(), col_strsplit(), col_substr(), col_substring()

Examples

col_align(red("foobar"), 20, "left")
col_align(red("foobar"), 20, "center")
col_align(red("foobar"), 20, "right")

Count number of characters in an ANSI colored string

Description

This is a color-aware counterpart of base::nchar(), which does not do well, since it also counts the ANSI control characters.

Usage

col_nchar(x, ...)

Arguments

Value

Numeric vector, the length of the strings in the character vector.

See Also

Other ANSI string operations: col_align(), col_strsplit(), col_substr(), col_substring()

Examples

str <- paste(
  red("red"),
  "default",
  green("green")
)

cat(str, "\n")
nchar(str)
col_nchar(str)
nchar(strip_style(str))

Split an ANSI colored string

Description

This is the color-aware counterpart of base::strsplit(). It works almost exactly like the original, but keeps the colors in the substrings.

Usage

col_strsplit(x, split, ...)

Arguments

Value

A list of the same length as x, the i-th element of which contains the vector of splits of x[i]. ANSI styles are retained.

See Also

Other ANSI string operations: col_align(), col_nchar(), col_substr(), col_substring()

Examples

str <- red("I am red---") %+%
  green("and I am green-") %+%
  underline("I underlined")

cat(str, "\n")

# split at dashes, keep color
cat(col_strsplit(str, "[-]+")[[1]], sep = "\n")
strsplit(strip_style(str), "[-]+")

# split to characters, keep color
cat(col_strsplit(str, "")[[1]], "\n", sep = " ")
strsplit(strip_style(str), "")

Substring(s) of an ANSI colored string

Description

This is a color-aware counterpart of base::substr(). It works exactly like the original, but keeps the colors in the substrings. The ANSI escape sequences are ignored when calculating the positions within the string.

Usage

col_substr(x, start, stop)

Arguments

Value

Character vector of the same length as x, containing the requested substrings. ANSI styles are retained.

See Also

Other ANSI string operations: col_align(), col_nchar(), col_strsplit(), col_substring()

Examples

str <- paste(
  red("red"),
  "default",
  green("green")
)

cat(str, "\n")
cat(col_substr(str, 1, 5), "\n")
cat(col_substr(str, 1, 15), "\n")
cat(col_substr(str, 3, 7), "\n")

substr(strip_style(str), 1, 5)
substr(strip_style(str), 1, 15)
substr(strip_style(str), 3, 7)

str2 <- "another " %+%
  red("multi-", sep = "", underline("style")) %+%
  " text"

cat(str2, "\n")
cat(col_substr(c(str, str2), c(3,5), c(7, 18)), sep = "\n")
substr(strip_style(c(str, str2)), c(3,5), c(7, 18))

Substring(s) of an ANSI colored string

Description

This is the color-aware counterpart of base::substring(). It works exactly like the original, but keeps the colors in the substrings. The ANSI escape sequences are ignored when calculating the positions within the string.

Usage

col_substring(text, first, last = 1000000L)

Arguments

Value

Character vector of the same length as x, containing the requested substrings. ANSI styles are retained.

See Also

Other ANSI string operations: col_align(), col_nchar(), col_strsplit(), col_substr()

Examples

str <- paste(
  red("red"),
  "default",
  green("green")
)

cat(str, "\n")
cat(col_substring(str, 1, 5), "\n")
cat(col_substring(str, 1, 15), "\n")
cat(col_substring(str, 3, 7), "\n")

substring(strip_style(str), 1, 5)
substring(strip_style(str), 1, 15)
substring(strip_style(str), 3, 7)

str2 <- "another " %+%
  red("multi-", sep = "", underline("style")) %+%
  " text"

cat(str2, "\n")
cat(col_substring(str2, c(3,5), c(7, 18)), sep = "\n")
substring(strip_style(str2), c(3,5), c(7, 18))

Combine two or more ANSI styles

Description

Combine two or more styles or style functions into a new style function that can be called on strings to style them.

Usage

combine_styles(...)

## S3 method for class 'crayon'
crayon$style

Arguments

Details

It does not usually make sense to combine two foreground colors (or two background colors), because only the first one applied will be used.

It does make sense to combine different kind of styles, e.g. background color, foreground color, bold font.

The $ operator can also be used to combine styles. Note that the left hand side of $ is a style function, and the right hand side is the name of a style in styles().

Value

The combined style function.

Examples

## Use style names
alert <- combine_styles("bold", "red4", "bgCyan")
cat(alert("Warning!"), "\n")

## Or style functions
alert <- combine_styles(bold, red, bgCyan)
cat(alert("Warning!"), "\n")

## Combine a composite style
alert <- combine_styles(bold, combine_styles(red, bgCyan))
cat(alert("Warning!"), "\n")

## Shorter notation
alert <- bold $ red $ bgCyan
cat(alert("Warning!"), "\n")

Concatenate character vectors

Description

The length of the two arguments must match, or one of them must be of length one. If the length of one argument is one, then the output's length will match the length of the other argument. See examples below.

Usage

lhs %+% rhs

Arguments

Value

Concatenated vectors.

Examples

"foo" %+% "bar"

letters[1:10] %+% chr(1:10)

letters[1:10] %+% "-" %+% chr(1:10)

## This is empty (unlike for parse)
character() %+% "*"

Remove a style

Description

Remove a style

Usage

drop_style(style)

Arguments

Value

Nothing.

See Also

Other styles: make_style()

Examples

make_style(new_style = "maroon", bg = TRUE)
cat(style("I am maroon", "new_style"), "\n")
drop_style("new_style")
"new_style" %in% names(styles())

Does the current R session support ANSI colors?

Description

From crayon 2.0.0, this function is simply a wrapper on num_ansi_colors().

Usage

has_color()

Value

TRUE if the current R session supports color.

Examples

has_color()

Check if a string has some ANSI styling

Description

Check if a string has some ANSI styling

Usage

has_style(string)

Arguments

Value

Logical vector, TRUE for the strings that have some ANSI styling.

Examples

## The second one has style if crayon is enabled
has_style("foobar")
has_style(red("foobar"))

Terminal Hyperlinks

Description

Terminal Hyperlinks

Usage

hyperlink(text, url)

has_hyperlink()

Arguments

Details

hyperlink()' creates an ANSI hyperlink.

has_hyperlink() checks if the current stdout() supports hyperlinks. terminal links.

See also https://gist.github.com/egmontkob/eb114294efbcd5adb1944c9f3cb5feda.

Value

Logical scalar, for has_hyperlink().

Examples

cat("This is an", hyperlink("R", "https://r-project.org"), "link.\n")
has_hyperlink()

Create an ANSI color style

Description

Create a style, or a style function, or both. This function is intended for those who wish to use 256 ANSI colors, instead of the more widely supported eight colors.

Usage

make_style(..., bg = FALSE, grey = FALSE, colors = num_colors())

Arguments

Details

The crayon package comes with predefined styles (see styles() for a list) and functions for the basic eight-color ANSI standard (red, blue, etc., see crayon).

There are no predefined styles or style functions for the 256 color ANSI mode, however, because we simply did not want to create that many styles and functions. Instead, make_style() can be used to create a style (or a style function, or both).

There are two ways to use this function:

1. If its first argument is not named, then it returns a function that can be used to color strings.

2. If its first argument is named, then it also creates a style with the given name. This style can be used in style(). One can still use the return value of the function, to create a style function.

The style (the ... argument) can be anything of the following:

• An R color name, see colors().

• A 6- or 8-digit hexa color string, e.g. ⁠#ff0000⁠ means red. Transparency (alpha channel) values are ignored.

• A one-column matrix with three rows for the red, green and blue channels, as returned by col2rgb (in the base grDevices package).

make_style() detects the number of colors to use automatically (this can be overridden using the colors argument). If the number of colors is less than 256 (detected or given), then it falls back to the color in the ANSI eight color mode that is closest to the specified (RGB or R) color.

See the examples below.

Value

A function that can be used to color strings.

See Also

Other styles: drop_style()

Examples

## Create a style function without creating a style
pink <- make_style("pink")
bgMaroon <- make_style(rgb(0.93, 0.19, 0.65), bg = TRUE)
cat(bgMaroon(pink("I am pink if your terminal wants it, too.\n")))

## Create a new style for pink and maroon background
make_style(pink = "pink")
make_style(bgMaroon = rgb(0.93, 0.19, 0.65), bg = TRUE)
"pink" %in% names(styles())
"bgMaroon" %in% names(styles())
cat(style("I am pink, too!\n", "pink", bg = "bgMaroon"))

Detect the number of ANSI colors to use

Description

Certain Unix and Windows terminals, and also certain R GUIs, e.g. RStudio, support styling terminal output using special control sequences (ANSI sequences).

num_ansi_colors() detects if the current R session supports ANSI sequences, and if it does how many colors are supported.

Usage

num_ansi_colors(stream = "auto")

detect_tty_colors()

Arguments

Details

The detection mechanism is quite involved and it is designed to work out of the box on most systems. If it does not work on your system, please report a bug. Setting options and environment variables to turn on ANSI support is error prone, because they are inherited in other environments, e.g. knitr, that might not have ANSI support.

If you want to turn off ANSI colors, set the NO_COLOR environment variable to a non-empty value.

The exact detection mechanism is as follows:

1. If the cli.num_colors options is set, that is returned.

2. If the R_CLI_NUM_COLORS environment variable is set to a non-empty value, then it is used.

3. If the crayon.enabled option is set to FALSE, 1L is returned. (This is for compatibility with code that uses the crayon package.)

4. If the crayon.enabled option is set to TRUE and the crayon.colors option is not set, then the value of the cli.default_num_colors option, or if it is unset, then 8L is returned.

5. If the crayon.enabled option is set to TRUE and the crayon.colors option is also set, then the latter is returned. (This is for compatibility with code that uses the crayon package.)

6. If the NO_COLOR environment variable is set, then 1L is returned.

7. If we are in knitr, then 1L is returned, to turn off colors in .Rmd chunks.

8. If stream is "auto" (the default) and there is an active sink (either for "output" or "message"), then we return 1L. (In theory we would only need to check the stream that will be be actually used, but there is no easy way to tell that.)

9. If stream is not "auto", but it is stderr() and there is an active sink for it, then 1L is returned. (If a sink is active for "output", then R changes the stdout() stream, so this check is not needed.)

10. If the cli.default_num_colors option is set, then we use that.

11. If R is running inside RGui on Windows, or R.app on macOS, then we return 1L.

12. If R is running inside RStudio, with color support, then the appropriate number of colors is returned, usually 256L.

13. If R is running on Windows, inside an Emacs version that is recent enough to support ANSI colors, then the value of the cli.default_num_colors option, or if unset 8L is returned. (On Windows, Emacs has isatty(stdout()) == FALSE, so we need to check for this here before dealing with terminals.)

14. If stream is not the standard output or standard error in a terminal, then 1L is returned.

15. Otherwise we use and cache the result of the terminal color detection (see below).

The terminal color detection algorithm:

1. If the COLORTERM environment variable is set to truecolor or ⁠24bit⁠, then we return 16 million colors.

2. If the COLORTERM environment variable is set to anything else, then we return the value of the cli.num_default_colors option, 8L if unset.

3. If R is running on Unix, inside an Emacs version that is recent enough to support ANSI colors, then the value of the cli.default_num_colors option is returned, or 8L if unset.

4. If we are on Windows in an RStudio terminal, then apparently we only have eight colors, but the cli.default_num_colors option can be used to override this.

5. If we are in a recent enough Windows 10 terminal, then there is either true color (from build 14931) or 256 color (from build 10586) support. You can also use the cli.default_num_colors option to override these.

6. If we are on Windows, under ConEmu or cmder, or ANSICON is loaded, then the value of cli.default_num_colors, or 8L if unset, is returned.

7. Otherwise if we are on Windows, return 1L.

8. Otherwise we are on Unix and try to run ⁠tput colors⁠ to determine the number of colors. If this succeeds, we return its return value. If the TERM environment variable is xterm and tput returned 8L, we return 256L, because xterm compatible terminals tend to support 256 colors (https://github.com/r-lib/crayon/issues/17) You can override this with the cli.default_num_colors option.

9. If TERM is set to dumb, we return 1L.

10. If TERM starts with screen, xterm, or vt100, we return 8L.

11. If TERM contains color, ansi, cygwin or linux, we return 8L.

12. Otherwise we return 1L.

Value

Integer, the number of ANSI colors the current R session supports for stream.

Examples

num_ansi_colors()

Number of colors the terminal supports

Description

From crayon version 2.0.0, this function is a simple wrapper on num_ansi_colors(), with the additional twist that the crayon.colors option is still obseved, and takes precedence, for compatibility.

Usage

num_colors(forget = FALSE)

Arguments

Value

Number of ANSI colors.

Examples

num_colors()

Show the ANSI color table on the screen

Description

Show the ANSI color table on the screen

Usage

show_ansi_colors(colors = num_colors())

Arguments

Value

The printed string, invisibly.

Switch on or off a style

Description

Make a style active. The text printed to the screen from now on will use this style.

Usage

## S3 method for class 'crayon'
start(x, ...)

finish(x, ...)

## S3 method for class 'crayon'
finish(x, ...)

Arguments

Details

This function is very rarely needed, e.g. for colored user input. For other reasons, just call the style as a function on the string.

Examples

## The input is red (if color is supported)
get_name <- function() {
  cat("Enter your name:", start(red))
  input <- readline()
  cat(finish(red))
  input
}
name <- get_name()
name

Remove ANSI escape sequences from a string

Description

Remove ANSI escape sequences from a string

Usage

strip_style(string)

Arguments

Value

The cleaned up string.

Examples

strip_style(red("foobar")) == "foobar"

Add style to a string

Description

See names(styles), or the crayon manual for available styles.

Usage

style(string, as = NULL, bg = NULL)

Arguments

Value

Styled character vector.

Examples

## These are equivalent
style("foobar", bold)
style("foobar", "bold")
bold("foobar")

ANSI escape sequences of crayon styles

Description

You can use this function to list all availables crayon styles, via names(styles()), or to explicitly apply an ANSI escape seauence to a string.

Usage

styles()

Value

A named list. Each list element is a list of two strings, named ‘open’ and ‘close’.

See Also

crayon() for the beginning of the crayon manual.

Examples

names(styles())
cat(styles()[["bold"]]$close)