DECSCA — Select Character Protection Attribute

Sequence	CSI <n> " q
Bytes	0x1B 0x5B <n> 0x22 0x71
Mnemonic	DECSCA
Otty support	✓

Description

Marks subsequently written characters as protected or erasable. Protected cells are skipped by the selective-erase sequences DECSED (CSI ? <n> J) and DECSEL (CSI ? <n> K); ordinary ED / EL ignore the attribute and erase everything.

<n>	Effect
0	Characters are erasable (default)
1	Characters are protected from selective erase
2	Characters are erasable (same as 0)

The attribute sticks to the cursor and applies to every character written until changed, so a typical use is "turn protection on, draw a fixed frame/labels, turn it off, then let the app selectively erase the editable region without disturbing the frame".

Interaction with other state

• Independent of SGR. SGR 0 (reset attributes) does not clear protection — only DECSCA 0 / 2, a soft reset (DECSTR), or a full reset (RIS) do.
• Saved with the cursor. DECSC / DECRC save and restore the protection state along with the cursor.
• Erasing a protected cell through any path leaves the replacement cell unprotected.

Example

# Draw a protected label, then prove a selective erase spares it.
printf '\e[2J\e[H'
printf '\e[1"q'        # protect on
printf 'LABEL: '
printf '\e[0"q'        # protect off
printf 'value-to-erase'
printf '\e[?2J'        # DECSED — 'value-to-erase' clears, 'LABEL: ' remains

Related

• ED — CSI ? <n> J is DECSED, the selective erase-in-display.
• EL — CSI ? <n> K is DECSEL, the selective erase-in-line.
• DECSTR — soft reset clears the protection attribute.