On Sat, May 4, 2019, 3:39 PM <benbe1...@gmx.net> wrote:
> Configuration Information [Automatically generated, do not change]:
> Machine: x86_64
> OS: linux-gnu
> Compiler: gcc
> Compilation CFLAGS: -DPROGRAM='bash' -DCONF_HOSTTYPE='x86_64'
> -DCONF_OSTYPE='linux-gnu' -DCONF_MACHTYPE='x86_64-pc-linux-gnu'
> -DCONF_VENDOR='pc' -DLOCALEDIR='/usr/share/locale' -DPACKAGE='bash' -DSHELL
> -DHAVE_CONFIG_H -I. -I../. -I.././include -I.././lib -Wdate-time
> -D_FORTIFY_SOURCE=2 -g -O2
> -fdebug-prefix-map=/build/bash-vEMnMR/bash-4.4.18=.
> -fstack-protector-strong -Wformat -Werror=format-security -Wall
> -Wno-parentheses -Wno-format-security
> uname output: Linux desktop 5.0.3-050003-generic #201903191333 SMP Tue Mar
> 19 13:35:24 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux
> Machine Type: x86_64-pc-linux-gnu
>
> Bash Version: 4.4
> Patch Level: 19
> Release Status: release
>
> Description:
> When setting up a complex PS1 prompt where parts of the
> prompt is expanded on every new prompt displayed by bash
> the escape sequences that are generated by that dynamic
> part are handled improperly (read: not at all).
>
> The desired behaviour should treat such escapes for e.g.
> the sequences \[ and \] equal both when the prompt expands
> to stuff\[stuff\]stuff, regardless of whether this was
> reached by "stuff$(echo \[stuff\])stuff" (\[\] handled) or
> reached by 'stuff$(echo \[stuff\])stuff' (not handled) being
> set as the value of PS1.
>
> Repeat-By:
> To demonstrate this odd behaviour assume some command
> that displays changing information at each invokation:
>
> __test1(){ echo -e "Random is \\[\e[37;1m\\]$RANDOM\e[0m"; }
>
> Now let's assume two cases:
>
> Case 1:
> PS1='Test$(__test1)Test\[\e[0m\]$ '
> -> Shows \[\] markers, includes output of $(__test1) dynamically
>
> Case 2:
> PS1="Test$(__test1)Test\[\e[0m\]$ "
> -> Displays correct, but statically includes output of $(__test1)
>
> The desired behaviour is dynamic inclusion of $(__test1) as with
> case 1 while having the \[\] markers respected as seen in case 2.
>
> Splitting the output of __test1 to separate sections with
> \[\] markers and such which don't need them is not possible,
> as the number of such sections may vary and the limited syntax
> of PS1 does not allow for loops and other conditional constructs
> on its top level.
>
> Also leaving out the \[\] markers from __test1 will cause the
> displayed prompt to misbehave.
>
> Fix:
> Move handling of \[ and \] markers to be done on the fully
> expanded, representation of the PS1 variable after variable
> substitutions and subshell output have been inserted.
>
I compute complex strings and assign PS1 within PROMPT_COMMAND rather than
expecting PS1's promptvars command substitution to do that - since
backslash escapes are done earlier. See "PROMPTING" in the man page where
the order of processing is described.
>
>
