std/tty

Put stdin in raw mode: keys arrive as they are pressed, with no echo and no line editing.

It also turns OFF signal generation, so Ctrl-C arrives as the byte 0x03 instead of killing the process. That is what keeps the terminal usable (a process killed mid-prompt would leave the shell with no echo) and it makes handling the cancellation the caller's job.

⚠️ Always pair it with defer raw_mode_end(). defer covers the normal return AND a panic (the runtime runs pending defers before aborting), which is the whole reason the restore does not need a signal handler. What it does not cover is a kill from outside the process; a shell's reset fixes that.

⚠️ On POSIX this goes through cfmakeraw, which also clears OPOST: a bare \n no longer returns the carriage. Print through raw_print between begin and end: println is only safe once the terminal is restored.

Restore the terminal state saved by raw_mode_begin. A no-op when raw mode is not installed, so an unpaired call is harmless.

Terminal width in columns, or 0 when it cannot be determined, not a terminal, or the query failed. A caller that needs a number anyway should pick its own default rather than treat 0 as a width.

Read the keys pressed so far, blocking until there is at least one.

Returns everything already queued, up to max bytes (capped at 64). Reading a BURST rather than a byte is what makes a lone Escape distinguishable from the start of an arrow sequence: the arrow's three bytes arrive in one call, Escape alone arrives as one byte. No timing is involved, and it behaves the same on POSIX and on a Windows console, whose keys arrive as the UTF-8 of what was typed whatever its code page.

Print s the way a raw-mode terminal needs, terminated.

raw_mode_begin clears OPOST on POSIX, so a bare \n advances a row without returning the carriage. s may be several lines: terminating only the last one leaves the rest climbing a staircase to the right.

True when stream is connected to an interactive terminal whose ANSI codes will render; defaults to stdout, so is_tty() checks stdout. On Windows this also enables virtual-terminal processing on the stream (and reports false when the console is too old to support it). The probe runs once per stream.

True when text beyond ASCII written to stream renders as such, so it may draw with box and shape glyphs. A POSIX terminal is taken as UTF-8. On Windows only a console renders it, print writing to one as text; a redirected stream gets bytes whose reader may decode them otherwise.

True when ANSI color should be emitted: either standard stream is a terminal and NO_COLOR is unset or empty. Per the NO_COLOR convention, a non-empty NO_COLOR value disables color regardless of its content.

s without the colour escapes the helpers here wrap text in, ESC [, a code and m: the text a reader sees, to measure or to compare.

Wrap s in an arbitrary SGR sequence code (e.g. "1;31") when coloring is enabled, else return s unchanged. Escape hatch for combinations the named helpers don't cover; prefer the named helpers for the common cases.

Reset all SGR attributes (SGR 0) when coloring is enabled, else "". Useful when composing sequences by hand.

Bold (SGR 1): emphasis, e.g. diagnostic codes.

Dim / faint (SGR 2). Renders on modern terminals; a no-op on consoles that don't support it (never raw escapes).

Italic (SGR 3). As dim, degrades to a no-op where unsupported.

Underline (SGR 4).

Reverse video: swap foreground and background (SGR 7).

Black foreground (SGR 30).

Red foreground (SGR 31): errors / failures.

Green foreground (SGR 32): successes.

Yellow foreground (SGR 33): warnings (the ANSI stand-in for orange).

Blue foreground (SGR 34).

Magenta foreground (SGR 35).

Cyan foreground (SGR 36).

White foreground (SGR 37).

Bright black / gray foreground (SGR 90).

Bright red foreground (SGR 91).

Bright green foreground (SGR 92).

Bright yellow foreground (SGR 93).

Bright blue foreground (SGR 94).

Bright magenta foreground (SGR 95).

Bright cyan foreground (SGR 96).

Bright white foreground (SGR 97).