Bash PS1 – Fix Hostname Not Updating After Script Change

bashshell

This is a copy of my post from stackoverflow; I realize I should have asked it here…

I want to run a script that changes the hostname and have my bash prompt (PS1 variable) update immediately with the proper hostname. How do I make this happen?

I run this

#!/bin/bash
# Usage: ./changehost <newhostname>

#Do two sed's to edit the files for persistent hostname change
sed -i s/$(hostname)/$1/g "/etc/hosts"
sed -i s/$(hostname)/$1/g "/etc/sysconfig/network"

#run the hostname command with new hostname to update it
hostname $1

In a terminal like so and get this

[user@host dir]# ./changehost newhostname
[user@host dir]#

But what I want is this

[user@host dir]# ./changehost newhostname
[user@newhostname dir]#

The terminal is updated properly only when I open up a new shell.

I have also tried to do 

export PS1='somestring'; export PS1='[\u@\h \W]\$'

outside of the script in the terminal and it does switch to 'somestring' and back, but the hostname is unchanged. :\

Is it possible that the \h is stored in memory when the process begins and can't be changed after startup?

Best Answer

If your PS1 is similar to:

export PS1='[\u@\h \W]\$'

The value of \h is only set on bash startup. Therefore, if you change the hostname, you need to start a new bash instance:

exec bash

Will replace bash by a new instance (with the value of \h updated). Sadly, it will exit a running script. Some other magic is needed to make the change for a shell script that follow executing code after the hostname change. I believe that it is not possible to keep the same script running with an updated hostname and \h. But I also believe that that is not what you are asking for.

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