Seulgi Kim

I've been writing a series of posts about CSI Sequences, but we rarely use CSI Sequences directly. However, there is a CSI Sequence that we use unknowingly. It's the clear command that clears the screen. The clear command basically uses two types of CSI sequences. One is CSI H ( Cu rsor P osition, a.k.a CUP); it moves the cursor to the beginning of the screen. The cursor is at the top-left corner after the command ends, thanks to CUP. The second CSI Sequence is CSI 2 J ( E rase in D isplay, a.k.a. ED), which is used to clear the entire screen. Linux and Mac use these two sequences; they behave the same way up to this point. However, Linux's clear and Mac's differ in their subsequent actions. In a nutshell, Linux's clear clears the scrollback buffer, while Mac's does not. Linux's one prints CSI 3 J after the two sequences. CSI 3 J is an extension of the Escape Sequence introduced by xterm that removes lines stored in the scrollback buffer. Since be...

Today, following my previous post , I will explain how to clear the screen using CSI Sequences. There are two sequences in the CSI Sequence for clearing. The first one is the Erase in Line sequence, called EL . It is composed of CSI # K ; it is used to erase lines, as the name suggests. If the # is not provided, the default value is 0, and if a value is provided, it must be one of the three: 0, 1, or 2. The terminal will ignore the sequence if any other value is provided. For example, if you print 0x311b5b334b32 (or 1^[3K2 ), the terminal ignores ^[3K , and the screen displays only 12 . The behavior of 0, 1, and 2 can be summarized as follows. 0 Erases from the cursor to the end of the line. 1 Erases from the beginning of the line to the cursor. 2 Erases the entire line, regardless of the cursor's position. Remember that the EL sequence does not move the cursor's position. Therefore, if you want to erase the current line and write a new line on the c...

Code Abbr Name CSI # A CUU CUrsor Up CSI # B CUD CUrsor Down CSI # C CUF CUrsor Forward CSI # D CUB CUrsor Backward CSI # E CNL CUrsor Next Line CSI # F CPL CUrsor Previous Line CSI # I CHT Cursor Horizontal forward Tabulation CSI # Z CBT Cursor Backward Tabulation CSI # G CHA Cursor Horizontal Absolute CSI # ; # H CUP CUrsor Position Today, we will continue from the  previous article to explore how to move the cursor using CSI sequences. The types of CSI sequences for moving the cursor can be summarized as follows. CUU, CUD, CUF, CUB These are the abbreviations for CUrsor Up, CUrsor Down, CUrsor Forward, and CUrsor Backward; as the names suggest, they move the cursor up, down, forward, and backward. They take a single number as an argument; if the argument is omitted, it is treated as 1. Thus, 0x1b[A is equivalent to 0x1b[1A . In this case, CUF and CUB move only within the same line. In other words, CUB rece...