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I need to get the value of the PS1 variable inside a bash script.

I know that running the script with a dot before makes bash pass env variables to the script, but I need to get PS1 regardless of how it is invoked, since I don't trust who will run the script.

How do I get it?

Update: the variable has been exported in /etc/profile, but I cannot get it:

[ Test ] root@myhost:~# export | grep PS1
declare -x PS1="[ Test ] \\u@\\h:\\w\\\$ "
[ Test ] root@myhost:~# cat test.sh 
echo $PS1
[ Test ] root@myhost:~# bash test.sh

I get no output from the last command.

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3 Answers 3

Reset to default
9

Start your test script with 'bash -i'; this makes it behave like a login shell and (amongst other things) sets PS1.

If your script will be run as an executable (.e.g ./test.sh) then you can also provide -i on the initial line, like this:

#!/bin/bash -i

Update: This only works if your script is executed directly, e.g.

$ ./test.sh

and not as:

$ bash test.sh

as that runs it in a non-interactive shell again. If you want to use bash from the command line, then do it like this:

$ bash -i test.sh
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4 Comments

Thanks, but it does not work. I created a test script with the suggested shebang header and a simple echo Prompt: $PS1, but I get the output Prompt: .
I get the $PS1 output from this.
Andrea: were you running the script with bash test.sh? See the update.
Note that this is not actually getting the "current" value for PS1, it is running the .bashrc file to generate a new value. This may be effectively what you want, but there is a distinction.
3

5 years later....because i used the following solution after finding this question.

If you want you can use the -i flag in the header and it seems to keep the environment during the script without having to run it in a special manner. I.e.

#!/bin/bash -i
echo "$PS1"

I don't know if this has any other weird behaviors, but it worked for what I needed.

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1 Comment

And 3 years later again, Note that this is not actually getting the "current" value for PS1, it is running the .bashrc file to generate a new value. This may be effectively what you want, but there is a distinction
2

This variable is somehow treated in a special way in bash (but eg in AIX or HPUX sh that i know you can access it even while non-interactive). It's being used only in interactive shell, so there's no possibility to get access to its value in non-interactive invocation.

Sorry, it's no answer, but that's how it is...

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3 Comments

Hi, can you provide a reference for your answer?
Found what I was searching for in man bash, section INVOCATION. You are right. Thanks!
@Andrea Spadaccini: Sorry, i've got some real life with no net access last weekend:) But you seem to have found your information, right?

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