[SOLVED] bash prompt: Can't change PS3

andrew.comly · 07-29-2015, 04:47 AM

I have copied the following shell script from my current bash textbook to make ~/bin/ps3.sh:

Code:

#/bin/bash

select i in mon tue wed exit
do
	case $i in
		mon) echo "Monday";;
		tue) echo "Tuesday";;
		wed) echo "Wednesday";;
		exit) exit;;
	esac
done

but when prompted for my selection, I only get the system default "#?". I want the prompt to be "Selection:" written in yellow, and then when I type in my answer the answer's color is again default. Even though I can successfully implement the export command to produce the prompt I want for PS1 and PS2, still PS3 simply doesn't work.

Code:

a@NP-NC110:~$ export PS3="\[\033[01;33m\]Selection: \[033[0m\]"
a@NP-NC110:~$ ps3.sh 
1) mon
2) tue
3) wed
4) exit
\[\033[01;33m\]Selection: \[033[0m\]

Even when I write

Code:

    PS3="\[\033[01;33m\]Selection: \[\033[0m\]"

in ~/.bashrc I still get the same prompt:

Code:

\[\033[01;33m\]Selection: \[033[0m\]

How can I get the prompt to be just the one word "Selection:" written in yellow w/o all the code surrounding it?

goumba · 07-29-2015, 05:08 AM

Give this one a try:

Code:

export PS3=$'\e[01;33mSelection: \e[0m'

\e is the same as \033

No idea why you have to use it that way for PS3, $ causes a string to be treated as an ANSI C string. See http://wiki.bash-hackers.org/syntax/quoting.

andrew.comly · 07-29-2015, 06:01 AM

Quote:

Originally Posted by goumba

Give this one a try:

Code:

export PS3=$'\e[01;33mSelection: \e[0m'

Awesome! It works. Strange how even though PS1 and PS2 follow one syntax, PS3 all of a sudden just follows another.

THANKS!!

andrew.comly · 07-29-2015, 08:14 AM

Quote:

Originally Posted by goumba

$ causes a string to be treated as an ANSI C string. See http://wiki.bash-hackers.org/syntax/quoting.

I've just completed the above tutorial. It was excellent, I've learned a lot. This syntax is far more robust than the regular type and "ANSI C like strings" syntax will be most useful in my future practice programs.

goumba · 07-29-2015, 01:12 PM

Great! Isn't that what you came here, was to learn a bit?

Glad it worked out for you on both fronts.

andrew.comly · 07-29-2015, 10:09 PM

Quote:

Originally Posted by goumba

Give this one a try:

Code:

export PS3=$'\e[01;33mSelection: \e[0m'

\e is the same as \033

Last night this worked. This morning I tried to use this $'\e method to simplify my ~/.bashrc configuration file. Now it doesn't work anymore, even when I change .bashrc back to it's original state. Currently my ~/.bashrc config file is:

Code:

RS="\[\033[0m\]"                    # reset
HC="\[\033[1m\]"                   # hicolor
FRED="\[\033[01;31m\]"      # foreground red
if [ "$color_prompt" = yes ]; then
    PS1="${debian_chroot:+($debian_chroot)}\[\033[01;31m\]\u\[\033[01;33m\]@\[\033[01;34m\]\h\[\033[01;33m\]:\[\033[01;35m\]\w\[\033[01;32m\]\$ $RS"
    PS2="\[\033[1m\]\[\033[01;34m\]>>\[\033[0m\]"
#\[\033[1m\] 
#PS2="$HC$FRED&gt; $RS"
    PS3=$'\e[01;33mSelection: \e[0m'
else
    PS1='${debian_chroot:+($debian_chroot)}\[\033[01;32m\]\u@\h\[\033[01;32m\]:\[\033[01;36m\]\w\[\033[01;33m\]\$ '
fi
unset color_prompt force_color_prompt

# If this is an xterm set the title to user@host:dir
case "$TERM" in
xterm*|rxvt*)
    PS1="\[\e]0;${debian_chroot:+($debian_chroot)}\u@\h: \w\a\]$PS1"
    ;;
*)
    ;;
esac

Code:

a@NP-NC110:~$ ps3.sh 
1) mon
2) tue
3) wed
4) exit
#?

Still the same "#?" prompt! I even rebooted, still the same thing.

Maybe it's because this $'\e technique only works during certain hours or days?

goumba · 07-29-2015, 10:25 PM

Quote:

Originally Posted by andrew.comly

Still the same "#?" prompt! I even rebooted, still the same thing.

Maybe it's because this $'\e technique only works during certain hours or days?

LOL. No.

Code:

PS3=$'\e[01;33m\]Selection: \e[0m\]'

Try that. You were missing the closing brackets.

andrew.comly · 07-29-2015, 11:02 PM

Quote:

Originally Posted by goumba

Code:

PS3=$'\e[01;33m\]Selection: \e[0m\]'

Try that. You were missing the closing brackets.

Doesn't work, specifically I change ~/.bashrc to:

Code:

PS3=$'\e[01;33m\]Selection: \e[0m\]'

and I still get:

Code:

a@NP-NC110:~$ ps3.sh 
1) mon
2) tue
3) wed
4) exit
#?

goumba · 07-29-2015, 11:32 PM

I just tried using your prompt, it works for me. Do you have PS3 defined anywhere else in .bashrc or .profile?

My apologies, an error in my last post, closing brackets are not needed.

Edit: Have you set color_prompt to "yes"? If color_prompt is not set to "yes" (usually by setting force_color_prompt to yes in .bashrc), then your PS3 assignment is being ignored. Certain terminal types will cause color_prompt to be set automatically by .bashrc, but in my experience it rarely happens and must be forced. If you don't want to force, can't force, then add a plain version, like so:

Code:

if [ "$color_prompt" = yes ]; then
    PS1="${debian_chroot:+($debian_chroot)}\[\033[01;31m\]\u\[\033[01;33m\]@\[\033[01;34m\]\h\[\033[01;33m\]:\[\033[01;35m\]\w\[\033[01;32m\]\$ $RS"
    PS2="\[\033[1m\]\[\033[01;34m\]>>\[\033[0m\]"
#\[\033[1m\] 
#PS2="$HC$FRED&gt; $RS"
    PS3=$'\e[01;33mSelection: \e[0m'
else
    PS1='${debian_chroot:+($debian_chroot)}\[\033[01;32m\]\u@\h\[\033[01;32m\]:\[\033[01;36m\]\w\[\033[01;33m\]\$ '
    PS3=$'Selection: '
fi

andrew.comly · 07-30-2015, 12:02 AM

Quote:

Originally Posted by goumba

Edit: Have you set color_prompt to "yes"? If color_prompt is not set to "yes" (usually by setting force_color_prompt to yes in .bashrc), then your PS3 assignment is being ignored.

My .bashrc is like follows - line 46-57:

Code:

	force_color_prompt=yes

if [ -n "$force_color_prompt" ]; then
    if [ -x /usr/bin/tput ] && tput setaf 1 >&/dev/null; then
	# We have color support; assume it's compliant with Ecma-48
	# (ISO/IEC-6429). (Lack of such support is extremely rare, and such
	# a case would tend to support setf rather than setaf.)
	color_prompt=yes
    else
	color_prompt=no
    fi
fi

and lines 80-98:

Code:

if [ "$color_prompt" = yes ]; then
    PS1="${debian_chroot:+($debian_chroot)}\[\033[01;31m\]\u\[\033[01;33m\]@\[\033[01;34m\]\h\[\033[01;33m\]:\[\033[01;35m\]\w\[\033[01;32m\]\$ $RS"
    PS2="\[\033[1m\]\[\033[01;34m\]>>\[\033[0m\]"
#\[\033[1m\] 
#PS2="$HC$FRED&gt; $RS"
    PS3=$'\e[01;33m\]Selection: \e[0m\]'
else
    PS1='${debian_chroot:+($debian_chroot)}\[\033[01;32m\]\u@\h\[\033[01;32m\]:\[\033[01;36m\]\w\[\033[01;33m\]\$ '
fi
unset color_prompt force_color_prompt

# If this is an xterm set the title to user@host:dir
case "$TERM" in
xterm*|rxvt*)
    PS1="\[\e]0;${debian_chroot:+($debian_chroot)}\u@\h: \w\a\]$PS1"
    ;;
*)
    ;;
esac

goumba · 07-30-2015, 12:09 AM

It's hard to say, unless for some reason color_prompt=yes is being ignored.

The odd thing is you have a prompt (PS1) with escape color codes that is being used when color_prompt is set to no, which would make it difficult to see which branch is being executed on your machine, because either way you're setting PS1 to include color codes (which is wrong, as if the terminal doesn't support colors it will print the codes and look like a lot of garbage).

It should look like:

Code:

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

Now, if you get an uncolored "Selection:" we'll know color_prompt is being ignored and can investigate that further.

Edit: Another option, I don't know if you're aware, is to set PS3 in the script itself, if you don't want that prompt for every time select is used.

Code:

#/bin/bash
PS3=$'\[\e33;1mSelection: \[\e0m'

select i in mon tue wed exit
do
	case $i in
		mon) echo "Monday";;
		tue) echo "Tuesday";;
		wed) echo "Wednesday";;
		exit) exit;;
	esac
done

When the script is completed, PS3 returns to the default (unless you export PS3).

andrew.comly · 07-30-2015, 12:20 AM

the line 85:

Code:

PS3=$'\e[01;33m\]Selection: \e[0m\]'

is the only instance of "PS3"

andrew.comly · 07-30-2015, 12:38 AM

Quote:

Originally Posted by goumba

It's hard to say, unless for some reason color_prompt=yes is being ignored.

The odd thing is you have a prompt (PS1) with escape color codes that is being used when color_prompt is set to no, which would make it difficult to see which branch is being executed on your machine, because either way you're setting PS1 to include color codes (which is wrong, as if the terminal doesn't support colors it will print the codes and look like a lot of garbage).

I too, found the section:

Code:

    PS1="${debian_chroot:+($debian_chroot)}\[\033[01;31m\]\u\[\033[01;33m\]@\[\033[01;34m\]\h\[\033[01;33m\]:\[\033[01;35m\]\w\[\033[01;32m\]\$ $RS"
    PS2="\[\033[1m\]\[\033[01;34m\]>>\[\033[0m\]"
    PS3=$'\e[01;33m\]Selection: \e[0m\]'
else
    PS1='${debian_chroot:+($debian_chroot)}\[\033[01;32m\]\u@\h\[\033[01;32m\]:\[\033[01;36m\]\w\[\033[01;33m\]\$ '

especially:

Code:

PS1='${debian_chroot:+($debian_chroot)}

really weird. Being that I didn't add this, I guess this is just the default .bashrc in Lubuntu 14.04.

I wonder what ${debian_chroot:+($debian_chroot)} means?

goumba · 07-30-2015, 12:44 AM

I understood that much.

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

andrew.comly · 07-30-2015, 12:49 AM

Quote:

Originally Posted by goumba

It should look like:

Code:

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

Now, if you get an uncolored "Selection:" we'll know color_prompt is being ignored and can investigate that further.

I changed my ~/.bashrc config file to:

Code:

if [ "$color_prompt" = yes ]; then
    PS1='${debian_chroot:+($debian_chroot)}\[\033[01;32m\]\u@\h\[\033[00m\]:\[\033[01;34m\]\w\[\033[00m\]\$ '
    PS2="\[\033[1m\]\[\033[01;34m\]>>\[\033[0m\]"
    PS3=$'\e[01;33mSelection: \e[0m'
else
    PS1='${debian_chroot:+($debian_chroot)}\u@\h:\w\$ '
    PS3='Selection: '
fi

and I still get:

Code:

a@NP-NC110:~$ ps3.sh 
1) mon
2) tue
3) wed
4) exit
#?

I guess I really am quite talentless. Nevertheless, I must keep trying.