Single Shift / Locking Shift family — SS2 / SS3 / LS2 / LS3 / LS1R / LS2R / LS3R

ISO 2022 character-set switching: invoke G2 / G3 once (SS2 / SS3), or lock GL / GR to a different G-set (LS2 / LS3 / LS1R / LS2R / LS3R). Pairs with \x1b( / \x1b) / \x1b* / \x1b+ G-set designators.

Byte forms

Every common string-literal form so you can paste-and-search either direction.

\\x1b[\x1bN SS2 \x1bO SS3 \x1bn LS2 \x1bo LS3 \x1b~ LS1R \x1b} LS2R \x1b| LS3R

\\033[\033N / \033O / \033n / \033o / \033~ / \033} / \033|

\\e[\eN / \eO / \en / \eo / \e~ / \e} / \e|

ESC [ESC N / ESC O / ESC n / ESC o / ESC ~ / ESC } / ESC |

hex1b 4e / 1b 4f / 1b 6e / 1b 6f / 1b 7e / 1b 7d / 1b 7c

Description

The ISO 2022 / ECMA-35 character-set machinery uses four registers (G0, G1, G2, G3) each pointing at a designated character set, with two 'pointers' (GL = invoked for 0x20–0x7F, GR = invoked for 0xA0–0xFF) selecting which G-set is currently active for which byte range. The single-shift and locking-shift families switch the active mapping.

Designators (set what each G-register points at — covered separately, listed here for context): - \x1b(<final> — designate G0 (e.g. \x1b(0 = G0 → DEC Special Graphics, the line-drawing set) - \x1b)<final> — designate G1 - \x1b*<final> — designate G2 - \x1b+<final> — designate G3

Invokers (switch GL / GR to point at a different G-register — this entry): - SS2 \x1bN (ESC N) — *Single Shift 2* — the next single 7-bit byte is interpreted via G2, then GL reverts. Useful for inserting a single character from a designated set without locking. - SS3 \x1bO (ESC O) — *Single Shift 3* — same as SS2 but uses G3. Note: ESC O is also the SS3 prefix in many keypad / function key codes (\x1bOA = up-arrow in application mode — see keymap), which is the same SS3 in spirit. - LS2 \x1bn (ESC n) — *Locking Shift 2* — point GL at G2 until a subsequent shift. All subsequent 7-bit bytes go through G2. - LS3 \x1bo (ESC o) — *Locking Shift 3* — point GL at G3. - LS1R \x1b~ (ESC ~) — *Locking Shift 1 Right* — point GR at G1 (8-bit byte range 0xA0–0xFF flows through G1). - LS2R \x1b} (ESC }) — *Locking Shift 2 Right* — point GR at G2. - LS3R \x1b| (ESC |) — *Locking Shift 3 Right* — point GR at G3. - (LS0 = \x0F SI and LS1 = \x0E SO are C0 single-byte controls — see c0-controls.)

Why you'd see these in the wild: 1. DEC line drawing — \x1b(0 designates G0 → DEC Special Graphics, then code 0x6C (l) renders as ┌. Frequently used by ncurses for box-drawing on non-UTF-8 terminals. 2. Legacy mainframe / serial-line apps that ship 7-bit binary 'paths' through GR-mapped G-sets to avoid 8-bit MSB-stripping middleware. 3. NRCS (National Replacement Character Sets) — e.g. \x1b)A designates G1 → UK NRCS (substitutes £ for #). 4. Telnet/SSH options for 7-bit data paths.

Modern UTF-8 era reality: ISO 2022 is largely vestigial. Terminals that announce UTF-8 (\x1b%G / \x1b%@ is the UTF-8 designate / leave-UTF-8 pair) typically interpret incoming bytes as UTF-8 and ignore SS2/SS3/LS2/LS3 entirely. The exception is DEC Special Graphics — kept alive because ncurses still emits \x1b(0 for line drawing on terminals that don't have full Unicode box glyphs.

Coverage: xterm = full (reference). kitty / WezTerm / iTerm2 / Ghostty / Konsole: support \x1b(0 line-drawing path; SS2/SS3/LS2/LS3/LS{1,2,3}R variously implemented but the practical use case is line drawing. gnome-terminal = full. Alacritty = partial (DEC Special Graphics + UTF-8 only). Linux console = partial (\x1b(0 works, more exotic invokers are no-ops). Windows Terminal / cmd / ConPTY: line-drawing via \x1b(0 partial; locking-shift right (\x1b~/\x1b}/\x1b|) no-op. macOS Terminal = partial. Don't rely on anything beyond DEC Special Graphics + designators unless you've specifically probed.

Spec citation: ISO 2022 / ECMA-35 / xterm-ctlseqs (Single Shift + Locking Shift family)

Examples

bash

# DEC line-drawing top-left corner: designate G0 -> SpecGraphics, emit 'l', restore.\nprintf '\\033(0l\\033(B'   # 'l' renders as ┌; \\033(B restores G0 -> US-ASCII

python

# Box from DEC special graphics: ┌──┐ / │  │ / └──┘\nimport sys\nsys.stdout.write('\\x1b(0lqqk\\nx  x\\nmqqj\\x1b(B\\n')\nsys.stdout.flush()

// Single-shift: print one G2 char without locking.\n// (G2 designated to DEC special graphics first.)\nfmt.Print(\"\\x1b*0\")   // designate G2 -> SpecGraphics\nfmt.Print(\"\\x1bNl\")    // SS2 then 'l' -> single ┌\nfmt.Print(\"X\")          // back to GL=G0 (US-ASCII) -> literal 'X'

javascript

// Lock GR to G2 for an 8-bit data path. Reset with LS0 (SI = \\x0f).\nprocess.stdout.write('\\x1b*A\\x1b}');  // G2 -> UK NRCS, LS2R\n// ... write 8-bit bytes; £ now lives at 0xA3 via G2\nprocess.stdout.write('\\x1b~');           // LS1R back to G1 default

/* ncurses-style box-drawing entry; designate G0 to SpecGraphics. */\nprintf(\"\\x1b(0\");\nputs(\"lqqk\");  /* ┌──┐ */\nputs(\"x  x\");  /* │  │ */\nputs(\"mqqj\");  /* └──┘ */\nprintf(\"\\x1b(B\");                /* restore G0 to US-ASCII */

Terminal support

xterm: yes
Linux console (fbcon): partial
macOS Terminal.app: partial
iTerm2: partial
Windows Terminal: partial
cmd.exe / ConPTY: partial
kitty: partial
alacritty: partial
WezTerm: partial
Ghostty: partial
GNOME Terminal: yes
Konsole: partial
tmux: yes
GNU screen: yes

xterm	Linux console (fbcon)	macOS Terminal.app	iTerm2	Windows Terminal	cmd.exe / ConPTY	kitty	alacritty	WezTerm	Ghostty	GNOME Terminal	Konsole	tmux	GNU screen
yes	partial	partial	partial	partial	partial	partial	partial	partial	partial	yes	partial	yes	yes

Related sequences

In the family cookbook

ESC cookbook · 5. Locking shifts + the 8-bit C1 bridge — `\x1bn` / `\x1bo` / `\x1b|` and `\x80-\x9F`