[SOLVED] bash prompt: Can't change PS3

andrew.comly · 07-30-2015, 01:02 AM

Quote:

Originally Posted by goumba

Now, if I add export, the prompt works:

Code:

if [ "$color_prompt" = yes ]; then
    PS1='${debian_chroot:+($debian_chroot)}\[\033[01;32m\]\u@\h\[\033[00m\]:\[\033[01;34m\]\w\[\033[00m\]\$ '
    export PS3=$'\e[01;33mSelection: \e[0m'
else
    PS1='${debian_chroot:+($debian_chroot)}\u@\h:\w\$ '
    export PS3='Selection: '
fi

This works now, but after I added "export=" and saved, I then opened a new terminal and entered

Code:

openbox --reconfigure

This probably wouldn't matter. However I still wonder if this will still work in a few hours? And another thing, what is the meaning of:

Code:

{debian_chroot:+($debian_chroot)}

??

I guess I will wait 3 days this time to "Mark as solved". Haste makes waste.

goumba · 07-30-2015, 01:14 AM

I myself am curious as to why PS3 must be exported while PS1 not. I'm guessing it has to do with the nature of 'interactive' shells, but I'm no expert myself. Or perhaps, as it is expected to be used in the script with the select built-in, it does not normally get inherited by child processes.

andrew.comly · 07-30-2015, 03:15 AM

The shortform "'\e" method doesn't work for PS1:

Code:

PS1='${debian_chroot:+($debian_chroot)}\e[01;31m\u\e[01;33m@\e[01;34m\h\e[01;33m:\e[01;35m\w\e[01;32m\$ \e[00m'

When I replace the longform (that fixed my prompt , reply #16, 2 replies above) with the above line of shortform, this causes the caret to be stuck in the prompt. E.g. the cursor instead of being after the prompt is at the very 1st letter. You type and it ends up 'inserting(deleting)' out the prompt. Of course any shortform never works in as many situations nor is as robust as the longform.

Maybe did I type something wrong? Probably if I continue to read the bash textbook I'll find that the shortform above ('\e method) has some combination of two characters that I should have used a backslash along with a strong/weak quote to avoid expanding.

Happy bash reading!!

goumba · 07-30-2015, 03:29 AM

Quote:

Originally Posted by andrew.comly

The shortform "'\e" method doesn't work for PS1:

Code:

PS1='${debian_chroot:+($debian_chroot)}\e[01;31m\u\e[01;33m@\e[01;34m\h\e[01;33m:\e[01;35m\w\e[01;32m\$ \e[00m'

When I replace the longform (that fixed my prompt , reply #16, 2 replies above) with the above line of shortform, this causes the caret to be stuck in the prompt. E.g. the cursor instead of being after the prompt is at the very 1st letter. You type and it ends up 'inserting(deleting)' out the prompt. Of course any shortform never works in as many situations nor is as robust as the longform.

Maybe did I type something wrong? Probably if I continue to read the bash textbook I'll find that the shortform above ('\e method) has some combination of two characters that I should have used a backslash along with a strong/weak quote to avoid expanding.

No, you did not do anything wrong, technically.

I remember there being a quirk about PS1 and escape codes, and bash's handling of the length of a line. Argh, I can't remember exactly what it was right now, nor find the resource in which I read it. When I find it, I'll give the details here.

goumba · 07-30-2015, 03:31 AM

Found it:

http://mywiki.wooledge.org/BashFAQ/053

As you'll notice, PS1 as included in debian's default .bashrc escapes the color codes with \[ and \].

All together that FAQ is a good thing to get to know.

FWIW I use the termcap method (tput setaf etc...) as it supposedly has better compatibility than using the ANSI escape codes directly.