Is there a listing of the various escape codes and how they are represented in vim (and outside I suppose to)? For example:
^M -- newline
^@ -- NIL
etc.
It seems I always have trouble googling these to figure out what a particular code means (in this case, ^J).
The man page for ascii(7) helps.
While it doesn't list the combinations such as ^@ and ^J, it lists @ and the uppercase letters, then [, \, ], ^ and _, on the right column, aligned with the control symbols on the left column.
The former (@, uppercase letters and the other 5 symbols) have ASCII codes 0x40 through 0x5f, while the control characters have ASCII codes 0x00 through 0x1f. The Control key masks bit 0x40, so the end result of using it with those letters on the right is the corresponding control character on the left.
(The Control key also masks bit 0x20, which explains why lowercase characters, which are on the 0x60 through 0x7f range also produce the same control characters. 0x40 | 0x20 = 0x60 so that's what gets masked.)
In specific, ^J is NL, newline, also represented as "\n". It is the character used to indicate the end of a line in Unix file format.
^M is \r and ^J is \n. Finally, what's the convention of using ^ as a prefix for those characters, do you know why that is done in vim?
J being used (0x4A) instead of \n (0x0A) for this? ie., it seems like they are adding 0x40 (64) to the original hex code for its display? Here's an image: imgur.com/a/Wy9WQc2.
^J is "\n" and not "\r".
Commented
Jun 21, 2020 at 18:21
The Control key masks bit 0x40, so the end result of using it with those letters on the right is the corresponding control character on the left. so that it doesn't display the character basically "as-is", ie NUL for null.
\rbeing shown as^J, or maybe I'm not reading it correctly?^Jis actuallyLF(line-feed), which C-style escapes represent as\n. Similarly,^Mis actuallyCR(carriage-return), which is often seen as\r. So, 3 different notations. And it's easy to see by reading across two columns from J or M or @+64over what the code is -- i.e., NUL is 0, but represented as 64 --> @ ?