escape-sequence-example

an example to demo escape sequence

tags: learning terminal software

content

ESC = "\x1b"
 
# Clear screen and move cursor to (10, 10)
print(f"{ESC}[2J{ESC}[10;10H", end="", flush=True)
print("X", end="", flush=True)
 
time.sleep(1)
# Move cursor down 1 row
print(f"{ESC}[1B", end="", flush=True)
 
time.sleep(1)
# Move cursor down 1 row again
print(f"{ESC}[1B", end="", flush=True)

• this program sends bytes to stdout, and if i run this program in a terminal, terminal is the stdout

• terminal then interprets the bytes it receives:

  • receives \x1b[2J, terminal clears the screen
  • receives ESC[10;10H, terminal renders cursor at Row 10 Col 10
  • receives ESC[1B, terminal renders cursor 1 col down

• flush=True is needed because there’s no \n new line printed, and usually stdout is line-buffered (only sends out when there’s new line)

up

down

reference

• linux basic concepts