Terminal Compatibility

fish writes various control sequences to the terminal. Some must be implemented to enable basic functionality, while others enable optional features and may be ignored by the terminal.

The terminal must be able to parse Control Sequence Introducer (CSI) commands, Operating System Commands (OSC) and optionally Device Control Strings (DCS). These are defined by ECMA-48. If a valid CSI, OSC or DCS sequence does not represent a command implemented by the terminal, the terminal must ignore it.

Control sequences are denoted in a fish-like syntax. Special characters other than \ are not escaped. Spaces are only added for readability and are not part of the sequence. Placeholders are written as <Ps> for a number or <Pt> for an arbitrary printable string.

NOTE: fish does not rely on your system’s terminfo database. In this document, terminfo (TI) codes are included for reference only.

Required Commands

Sequence	TI	Description	Origin
\r	n/a	Move cursor to the beginning of the line
\n	cud1	Move cursor down one line.
\e[ Ps A	cuu	Move cursor up Ps columns, or one column if no parameter.	VT100
\e[ Ps C	cuf	Move cursor to the right Ps columns, or one column if no parameter.	VT100
\x08	cub1	Move cursor one column to the left.	VT100
\e[ Ps D	cub	Move cursor to the left Ps times.	VT100
\e[H	cup	Set cursor position (no parameters means: move to row 1, column 1).	VT100
\e[K	el	Clear to end of line.	VT100
\e[J	ed	Clear to the end of screen.	VT100
\e[2J	clear	Clear the screen.	VT100
\e[0c		Request primary device attribute. The terminal must respond with a CSI command that starts with the ? parameter byte (so a sequence starting with \e[?) and has c as final byte. Failure to implement this will cause a brief pause at startup followed by a warning. For the time being, both can be turned off by turning off the query-terminal feature flag.	VT100
n/a	am	Soft wrap text at screen width.
n/a	xenl	Printing to the last column does not move the cursor to the next line. Verify this by running printf %0"$COLUMNS"d 0; sleep 3

Optional Commands

Sequence	TI	Description	Origin
\t	it	Move the cursor to the next tab stop (à 8 columns). This is mainly relevant if your prompt includes tabs.
\e[m	sgr0	Turn off bold/dim/italic/underline/reverse attribute modes and select default colors.
\e[1m	bold	Enter bold mode.
\e[2m	dim	Enter dim mode.
\e[3m	sitm	Enter italic mode.
\e[4m	smul	Enter underline mode.
\e[4:2m	Su	Enter double underline mode.	kitty
\e[4:3m	Su	Enter curly underline mode.	kitty
\e[4:4m	Su	Enter dotted underline mode.	kitty
\e[4:5m	Su	Enter dashed underline mode.	kitty
\e[7m	rev	Enter reverse video mode (swap foreground and background colors).
\e[23m	ritm	Exit italic mode.
\e[24m	rmul	Exit underline mode.
\e[38;5; Ps m	setaf	Select foreground color Ps from the 256-color-palette.
\e[48;5; Ps m	setab	Select background color Ps from the 256-color-palette.
\e[58:5: Ps m (note: colons not semicolons)	Su	Select underline color Ps from the 256-color-palette.	kitty
\e[ Ps m	setaf setab	Select foreground/background color. This uses a color in the aforementioned 256-color-palette, based on the range that contains the parameter: 30-37 maps to foreground 0-7, 40-47 maps to background 0-7, 90-97 maps to foreground 8-15 and 100-107 maps to background 8-15.
\e[38;2; Ps ; Ps ; Ps m		Select foreground color from 24-bit RGB colors.
\e[48;2; Ps ; Ps ; Ps m		Select background color from 24-bit RGB colors.
\e[49m		Reset background color to the terminal’s default.
\e[58:2:: Ps : Ps : Ps m (note: colons not semicolons)	Su	Select underline color from 24-bit RGB colors.	kitty
\e[59m	Su	Reset underline color to the default (follow the foreground color).	kitty
\e[ Ps S	indn	Scroll up the content (not the viewport) Ps lines (called SCROLL UP / SU by ECMA-48 and “scroll forward” by terminfo). When fish detects support for this feature, status test-terminal-features scroll-content-up will return 0, which enables the ctrl-l binding to use the scrollback-push special input function.	ECMA-48
\e[= Ps u, \e[? Ps u	n/a	Enable the kitty keyboard protocol.	kitty
\e[6n	n/a	Request cursor position report. The response must be of the form \e[ Ps ; Ps R where the first parameter is the row number and the second parameter is the column number. Both start at 1. This is used by the scrollback-push special input function, and inside terminals that implement the OSC 133 click_events feature.	VT100
\e[ \x20 q	Se	Reset cursor style to the terminal’s default. This is not used as of today but may be in future.	VT520
\e[ Ps \x20 q	Ss	Set cursor style (DECSCUSR); Ps is 2, 4 or 6 for block, underscore or line shape.	VT520
\e[ Ps q	n/a	Request terminal name and version (XTVERSION). This is only used for temporary workarounds for incompatible terminals.	XTerm
\e[?25h	cvvis	Enable cursor visibility (DECTCEM).	VT220
\e[?1000l	n/a	Disable mouse reporting.	XTerm
\e[?1004h	n/a	Enable focus reporting.
\e[?1004l	n/a	Disable focus reporting.
\e[?1049h	n/a	Enable alternate screen buffer.	XTerm
\e[?1049l	n/a	Disable alternate screen buffer.	XTerm
\e[?2004h		Enable bracketed paste.	XTerm
\e[?2004l		Disable bracketed paste.	XTerm
\e]0; Pt \x07	ts	Set window title (OSC 0).	XTerm
\e]7;file:// Pt / Pt \x07		Report working directory (OSC 7). Since the terminal may be running on a different system than a (remote) shell, the hostname (first parameter) will not be localhost.	iTerm2
\e]8;; Pt \e\\		Create a hyperlink (OSC 8). This is used in fish’s man pages.	GNOME Terminal
\e]52;c; Pt \x07		Copy to clipboard (OSC 52). Used by fish_clipboard_copy.	XTerm
\e]133;A; click_events=1\x07		Mark prompt start (OSC 133), with kitty’s click_events extension. The click_events extension enables mouse clicks to move the cursor or select pager items, assuming that cursor position reporting is available.	FinalTerm, kitty
\e]133;C; cmdline_url= Pt \x07		Mark command start (OSC 133), with kitty’s cmdline_url extension whose parameter is the URL-encoded command line.	FinalTerm, kitty
\e]133;D; Ps \x07		Mark command end (OSC 133); Ps is the exit status.	FinalTerm
\eP+q Pt \e\\		Request terminfo capability (XTGETTCAP). The parameter is the capability’s hex-encoded terminfo code. To advertise a capability, the response must be of the form \eP1+q Pt \e\\ or \eP1+q Pt = Pt \e\\. In either variant the first parameter must be the hex-encoded terminfo code. The second variant’s second parameter is ignored. Currently, fish only queries the indn string capability.	XTerm (but without string capabilities), kitty; also adopted by foot, wezterm, contour, ghostty

DCS commands and GNU screen

Fully-correct DCS parsing is optional because fish switches to the alternate screen before printing any DCS commands. However, since GNU screen neither allows turning on the alternate screen buffer by default, nor treats DCS commands in a compatible way, fish’s initial prompt may be garbled by a DCS payload like +q696e646e. For the time being, fish works around this by checking for presence of the STY environment variable. If that doesn’t work for some reason, you can add this to your ~/.screenrc:

altscreen on

Or add this to your config.fish:

function GNU-screen-workaround --on-event fish_prompt
    commandline -f repaint
    functions --erase GNU-screen-workaround
end