ANSIEscapeCodes

ANSIEscapeCodes are a family of in-band control sequences used to control formatting, color, and cursor movement in text terminals and terminal emulators. They originated in the ANSI X3.64 standard (also known as ECMA-48 and ISO/IEC 6429) and are transmitted as sequences starting with the escape character. The most common subset is the CSI, or Control Sequence Introducer, which uses ESC followed by [ and then parameters and a final byte that selects the command. The Select Graphic Rendition (SGR) subset is widely used to set text attributes such as color and style.

SGR sequences enable a range of effects. For example, ESC [ 0 m resets attributes, ESC [ 1 m enables bold, ESC [ 3 m enables italic, and ESC [ 4 m underlines text. Colors can be set with 38 and 48 parameters: ESC [ 38;5; n m selects a 256-color foreground, ESC [ 48;5; n m selects a 256-color background. For true color, ESC [ 38;2; R;G;B m and ESC [ 48;2; R;G;B m specify 24-bit RGB colors for foreground and background, respectively.

In addition to styling, CSI sequences control cursor position and screen manipulation. Examples include ESC [ 2 J to clear the screen, ESC [ H to move the cursor to the home position, and ESC [ n ; m H to position the cursor. Operating System Command (OSC) sequences cover non-printing actions such as setting the window title, for example ESC ] 0 ; title BEL.

Usage and portability vary by terminal. Most Unix-like terminals and modern terminal emulators support ANSI escape codes, but there are differences in color depth support and compatibility with older systems. Terminfo and termcap databases describe terminal capabilities to aid portable use.