Changing bash prompt in new bash

The prompt is defined by the PS1, PS2, PS3 and PS4 environment variables. So, e.g. the following will start a new bash with the prompt set to "foo: ":

PS1="foo: " bash --norc

The --norc is required to suppress processing of the initialization files, which would override the PS1 variable.

I have the same problem - I'd like to startup a temporary bash from the command line; and while most other environment variables remain; those that are sourced from ~/.bashrc are kind of difficult to override - especially if you, like me, would actually like to keep the ~/.bashrc you already have (and aliases inside, etc.) - save for the PS1 prompt.

Here is something that works for me (note that --init-file is a synonym/alias for --rcfile):

bash --rcfile <(cat ~/.bashrc ; echo 'PS1="\[\033[0;33m\]\u@HELLO:\W\$\[\033[00m\] "')

Basically, the bracket/less-than + parenthesis idiom <() starts up bash process substitution; everything echoed to stdout inside the parenthesis will end up in a temporary file, /dev/fd/<n>. So we first cat the contents of out ~/.bashrc; then we simply add a PS1 set command at end, (which effectively overrides) - this ends up in /dev/fd/<n>; and bash then uses /dev/fd/<n> for the new rcfile.

This is how it behaves:

user@pc:tmp$ TESTVAR="testing" bash --rcfile <(cat ~/.bashrc ; echo 'PS1="\[\033[0;33m\]\u@HELLO:\W\$\[\033[00m\] "')user@HELLO:tmp$ test-alias-tab-completion ^Cuser@HELLO:tmp$ echo $TESTVAR testinguser@HELLO:tmp$ exitexituser@pc:tmp$ 

You can set an environment variable, and then use that environment variable in your prompt in .bashrc.