BS

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Standard

BS (Backspace) is a C0 control character that moves the cursor one position to the left. It is one of the oldest control characters, present since the original ASCII standard.

Syntax

BS        0x08

Formal syntax

BS = 0x08 ;

Description

Per ECMA-48 §8.3.5, BS "causes the active data position to be moved one character position in the data component in the direction opposite to that of the implicit movement."

In standard terminal usage with left-to-right writing, this means the cursor moves one column to the left. The character at the cursor position is not erased — BS only moves the cursor. To delete a character, a terminal application typically sends BS SP BS (backspace, space, backspace) to overwrite the character with a space.

If the cursor is already at the left margin (column 1), BS has no effect. BS does not wrap to the previous line.

note

In the context of a line discipline (e.g., canonical mode in Unix), the kernel's terminal driver typically interprets the erase character (often mapped to backspace) by sending BS SP BS to the terminal. The BS control character itself only moves the cursor.

Examples

printf 'ABC\b\b'    # Prints "ABC" then moves cursor back to 'B'
printf 'AB\b \bA'   # Prints "AB", erases 'B', prints 'A' → "AA"

Specifications

Specification	Section
ECMA-48	§8.3.5

Terminal support

Terminal	Support	Version	Notes
Terminal Emulators
Alacritty	✓	Yes	Handler backspace() at term/mod.rs:1398
Bobcat	✓	0.9.0	Basic C0 control, handled in TerminalCtrl library
contour	✓	v0.1.0	Implemented in executeControlCode; calls backspace()
foot	✓	Yes	Implemented in vt.c:136-166 with reverse wrap support
Ghostty	✓	v1.0.0	Handled in stream.zig:768 as C0.BS (0x08)
iTerm2	✓	Yes
Kitty	✓	Yes
Konsole	✓	Yes
mintty	✓	Yes	Handled in do_ctrl() at src/termout.c:1691
mlterm	✓	rel-0_2_1
PuTTY	✓	0.45
Rio	✓	v0.0.28
rxvt-unicode	✓	rxvt-unicode-1.2
st	✓	0.6
terminology	✓	v0.1.0
VT100	✓	Yes
VTE	✓	Yes
WezTerm	✓	Yes	Handled in performer.rs:414 via ControlCode::Backspace, implements reverse-wraparound mode
Windows Terminal	✓	Yes	Handled via CursorBackward(1) dispatch in OutputStateMachineEngine.cpp:59-60
xterm	✓	Yes	Implemented in charproc.c:3701. Moves cursor left via CursorBack()
xterm.js	✓	2.3.0
Multiplexers
cy	✓	v0.1.0
GNU Screen	✓	v.4.2.0	Implemented in Special() function at src/ansi.c:678
tmux	✓	0.8	Implemented via screen_write_backspace()
tuios	✓	v0.0.15
Zellij	✓	v0.5.0-beta

See also

• CUU/CUD/CUF/CUB — Cursor Movement — CSI-based cursor movement sequences