termenv lets you safely use advanced styling options on the terminal. It gathers information about the terminal environment in terms of its ANSI & color support and offers you convenient methods to colorize and style your output, without you having to deal with all kinds of weird ANSI escape sequences and color conversions.

Features

• RGB/TrueColor support
• Detects the supported color range of your terminal
• Automatically converts colors to the best matching, available colors
• Terminal theme (light/dark) detection
• Chainable syntax
• Nested styles

Installation

go get github.com/muesli/termenv

Usage

output := termenv.NewOutput(os.Stdout)

termenv queries the terminal's capabilities it is running in, so you can safely use advanced features, like RGB colors or ANSI styles. output.Profile returns the supported profile:

• termenv.Ascii - no ANSI support detected, ASCII only
• termenv.ANSI - 16 color ANSI support
• termenv.ANSI256 - Extended 256 color ANSI support
• termenv.TrueColor - RGB/TrueColor support

Alternatively, you can use termenv.EnvColorProfile which evaluates the terminal like ColorProfile, but also respects the NO_COLOR and CLICOLOR_FORCE environment variables.

You can also query the terminal for its color scheme, so you know whether your app is running in a light- or dark-themed environment:

// Returns terminal's foreground color
color := output.ForegroundColor()

// Returns terminal's background color
color := output.BackgroundColor()

// Returns whether terminal uses a dark-ish background
darkTheme := output.HasDarkBackground()

Manual Profile Selection

If you don't want to rely on the automatic detection, you can manually select the profile you want to use:

output := termenv.NewOutput(os.Stdout, termenv.WithProfile(termenv.TrueColor))

Colors

termenv supports multiple color profiles: Ascii (black & white only), ANSI (16 colors), ANSI Extended (256 colors), and TrueColor (24-bit RGB). Colors will automatically be degraded to the best matching available color in the desired profile:

TrueColor => ANSI 256 Colors => ANSI 16 Colors => Ascii

s := output.String("Hello World")

// Supports hex values
// Will automatically degrade colors on terminals not supporting RGB
s.Foreground(output.Color("#abcdef"))
// but also supports ANSI colors (0-255)
s.Background(output.Color("69"))
// ...or the color.Color interface
s.Foreground(output.FromColor(color.RGBA{255, 128, 0, 255}))

// Combine fore- & background colors
s.Foreground(output.Color("#ffffff")).Background(output.Color("#0000ff"))

// Supports the fmt.Stringer interface
fmt.Println(s)

Styles

You can use a chainable syntax to compose your own styles:

s := output.String("foobar")

// Text styles
s.Bold()
s.Faint()
s.Italic()
s.CrossOut()
s.Underline()
s.Overline()

// Reverse swaps current fore- & background colors
s.Reverse()

// Blinking text
s.Blink()

// Combine multiple options
s.Bold().Underline()

Template Helpers

termenv provides a set of helper functions to style your Go templates:

// load template helpers
f := output.TemplateFuncs()
tpl := template.New("tpl").Funcs(f)

// apply bold style in a template
bold := `{{ Bold "Hello World" }}`

// examples for colorized templates
col := `{{ Color "#ff0000" "#0000ff" "Red on Blue" }}`
fg := `{{ Foreground "#ff0000" "Red Foreground" }}`
bg := `{{ Background "#0000ff" "Blue Background" }}`

// wrap styles
wrap := `{{ Bold (Underline "Hello World") }}`

// parse and render
tpl, err = tpl.Parse(bold)

var buf bytes.Buffer
tpl.Execute(&buf, nil)
fmt.Println(&buf)

Other available helper functions are: Faint, Italic, CrossOut, Underline, Overline, Reverse, and Blink.

Positioning

// Move the cursor to a given position
output.MoveCursor(row, column)

// Save the cursor position
output.SaveCursorPosition()

// Restore a saved cursor position
output.RestoreCursorPosition()

// Move the cursor up a given number of lines
output.CursorUp(n)

// Move the cursor down a given number of lines
output.CursorDown(n)

// Move the cursor up a given number of lines
output.CursorForward(n)

// Move the cursor backwards a given number of cells
output.CursorBack(n)

// Move the cursor down a given number of lines and place it at the beginning
// of the line
output.CursorNextLine(n)

// Move the cursor up a given number of lines and place it at the beginning of
// the line
output.CursorPrevLine(n)

Screen

// Reset the terminal to its default style, removing any active styles
output.Reset()

// RestoreScreen restores a previously saved screen state
output.RestoreScreen()

// SaveScreen saves the screen state
output.SaveScreen()

// Switch to the altscreen. The former view can be restored with ExitAltScreen()
output.AltScreen()

// Exit the altscreen and return to the former terminal view
output.ExitAltScreen()

// Clear the visible portion of the terminal
output.ClearScreen()

// Clear the current line
output.ClearLine()

// Clear a given number of lines
output.ClearLines(n)

// Set the scrolling region of the terminal
output.ChangeScrollingRegion(top, bottom)

// Insert the given number of lines at the top of the scrollable region, pushing
// lines below down
output.InsertLines(n)

// Delete the given number of lines, pulling any lines in the scrollable region
// below up
output.DeleteLines(n)

Session

// SetWindowTitle sets the terminal window title
output.SetWindowTitle(title)

// SetForegroundColor sets the default foreground color
output.SetForegroundColor(color)

// SetBackgroundColor sets the default background color
output.SetBackgroundColor(color)

// SetCursorColor sets the cursor color
output.SetCursorColor(color)

// Hide the cursor
output.HideCursor()

// Show the cursor
output.ShowCursor()

// Copy to clipboard
output.Copy(message)

// Copy to primary clipboard (X11)
output.CopyPrimary(message)

// Trigger notification
output.Notify(title, body)

Mouse

// Enable X10 mouse mode, only button press events are sent
output.EnableMousePress()

// Disable X10 mouse mode
output.DisableMousePress()

// Enable Mouse Tracking mode
output.EnableMouse()

// Disable Mouse Tracking mode
output.DisableMouse()

// Enable Hilite Mouse Tracking mode
output.EnableMouseHilite()

// Disable Hilite Mouse Tracking mode
output.DisableMouseHilite()

// Enable Cell Motion Mouse Tracking mode
output.EnableMouseCellMotion()

// Disable Cell Motion Mouse Tracking mode
output.DisableMouseCellMotion()

// Enable All Motion Mouse mode
output.EnableMouseAllMotion()

// Disable All Motion Mouse mode
output.DisableMouseAllMotion()

Bracketed Paste

// Enables bracketed paste mode
termenv.EnableBracketedPaste()

// Disables bracketed paste mode
termenv.DisableBracketedPaste()

Terminal Feature Support

Color Support

• 24-bit (RGB): alacritty, foot, iTerm, kitty, Konsole, st, tmux, vte-based, wezterm, Ghostty, Windows Terminal
• 8-bit (256): rxvt, screen, xterm, Apple Terminal
• 4-bit (16): Linux Console

Control Sequences

System Commands

Platform Support

termenv works on Unix systems (like Linux, macOS, or BSD) and Windows. While terminal applications on Unix support ANSI styling out-of-the-box, on Windows you need to enable ANSI processing in your application first:

    restoreConsole, err := termenv.EnableVirtualTerminalProcessing(termenv.DefaultOutput())
    if err != nil {
        panic(err)
    }
    defer restoreConsole()

The above code is safe to include on non-Windows systems or when os.Stdout does not refer to a terminal (e.g. in tests).

Color Chart

You can find the source code used to create this chart in termenv's examples.

Related Projects

• reflow - ANSI-aware text operations
• Lip Gloss - style definitions for nice terminal layouts 👄
• ansi - ANSI sequence helpers

termenv in the Wild

Need some inspiration or just want to see how others are using termenv? Check out these projects:

• Bubble Tea - a powerful little TUI framework 🏗
• Glamour - stylesheet-based markdown rendering for your CLI apps 💇🏻‍♀️
• Glow - a markdown renderer for the command-line 💅🏻
• duf - Disk Usage/Free Utility - a better 'df' alternative
• gitty - contextual information about your git projects
• slides - terminal-based presentation tool

Feedback

Got some feedback or suggestions? Please open an issue or drop me a note!

• Twitter
• The Fediverse

License

MIT