.bashrc edit messes up terminal command arrow-up history print

Question

I wanted to give my terminal prompt in Ubuntu a more personal look, and wanted to change the text prior to the '$' when writing a command.

From what I've found this is done by editing the .bashrc file in the home directory, so I went in there and changed

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

to

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

This works and the terminal looks the way I want it to.

But after some time when entering a couple of commands when I use the arrow-up key to get to the command history, things get weird.

From a clean line and pressing the arrow-up key is works. When pressing it again the text that was on the line gets capped at about ~15 characters and the new command in the history (that is supposed to be displayed) gets capped by a few characters in the beginning, and they are sort of merged together on the command line.

E.g. my two most recent commands are

Java Test4 words-250.txt words-250-in.txt
Javac Test4.java

When pressing the arrow-up key once, the first line is displayed, as it should. When pressing it a second time, this is displayed:

Java Test4 worc Test4.java

Despite this weird output, the terminal works fine. If for instance I press enter after doing the above, Javac Test4.java will run. If I instead try to delete the entire line using backspace, I am only able to delete up until the line says

Java Test4

and if pressing enter after that I get a new empty line, just as if the line was empty when pressing enter.

All of this goes away if I reset the .bashrc file.

Why does this happen and how can I fix it?

Answer 1

You need to enclose the escape sequences in \[...\], to tell bash not to count them while determining the prompt width. Otherwise, bash thinks the prompt is longer than the actual displayed length (because the escape sequences don't consume any visible space).

So, adapting the other prompt:

PS1='\[\033[1;32m\][\W]\$ \[\033[00m\]'

Both the above PS1 and the following would work equally well:

PS1='\[\e[1;32m\][\W]\$ \[\e[m\]'