sh: Allow an ASCII ESC in PS
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Authored by otis on Dec 14 2022, 4:03 PM.

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jilles
pstef

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Summary

Introduce new prompt format character, '\e' that emits an ASCII ESC
character. This might come handy to use ANSI sequences in PS1, for
example.

Example in ~/.shrc:

PS1="\e[7m\u@\h\e[0m:\w \\$ "

This is my naive approach, as this solves my use case.

Repository

rG FreeBSD src repository

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Buildable 48720
Build 45606: arc lint + arc unit

otis requested review of this revision.Dec 14 2022, 4:03 PM

Adding support for escape sequences might make it important to increase PROMPTLEN.

bin/sh/parser.c
2067–2069	The `\001` codes for `EL_PROMPT_ESC` need to be around the whole escape sequence, not just the character with code 27, so that libedit's idea of the cursor position remains correct. This is like bash's `\[` and `\]`. Consideration: patch libedit instead so it knows how long escape sequences are (`\033[` "CSI" sequences end with certain characters, `\033]` "OSC" sequences end with `\033\\` or `\007`, perhaps a bit more). Terminals should be sufficiently consistent now, and this relieves the user from adding special sequences to the prompt.
2069	The above check `i < PROMPTLEN - 1` is not sufficient to prevent overflow here.

This revision now requires changes to proceed.Dec 14 2022, 5:06 PM

Try with '\[' and '\]'

otis marked 2 inline comments as done.Dec 14 2022, 7:56 PM

jilles requested changes to this revision.Dec 18 2022, 9:04 PM

jilles added inline comments.

bin/sh/parser.c
2070	Adding the ESC character implicitly from `\[` makes some sense in a vacuum, but it's not compatible with bash (in neither direction), so I don't like it. A simple solution would be to make `\[` and `\]` generate `\001` and add `\e` as before.