Put terminal in raw mode, clear the screen, run some code. Reset the terminal to original mode when the code finish running.

runInRawMode.swift

#if canImport(Darwin)
import Darwin
#else
import Glibc
#endif

enum RawModeError: Error {
    case notATerminal
    case failedToGetTerminalSetting
    case failedToSetTerminalSetting
}

func runInRawMode(_ task: @escaping () throws -> Void) throws {
    var originalTermSetting = termios()
    guard isatty(STDIN_FILENO) != 0 else {
        throw RawModeError.notATerminal
    }

    guard tcgetattr(STDIN_FILENO, &originalTermSetting) >= 0 else {
        throw RawModeError.failedToGetTerminalSetting
    }


    var raw = originalTermSetting
    raw.c_iflag &= ~(UInt(BRKINT) | UInt(ICRNL) | UInt(INPCK) | UInt(ISTRIP) | UInt(IXON))
    raw.c_oflag &= ~(UInt(OPOST))
    raw.c_cflag |= UInt(CS8)
    raw.c_lflag &= ~(UInt(ECHO) | UInt(ICANON) | UInt(IEXTEN) | UInt(ISIG))
    raw.c_cc.16 = 0
    raw.c_cc.17 = 1

    guard tcsetattr(STDIN_FILENO, TCSAFLUSH, &raw) >= 0 else {
        throw RawModeError.failedToSetTerminalSetting
    }

    defer {
        tcsetattr(STDIN_FILENO, TCSAFLUSH, &originalTermSetting)
    }

    print("\u{1b}[2J")

    try task()
}

// Example usage: run a loop until 'q' is pressed
let q = Character("q").asciiValue!
try runInRawMode {
    while true {
        var char: UInt8 = 0
        read(STDIN_FILENO, &char, 1)
        if char == q {
            exit(0)
        }
    }
}