shell scripting question

ron7000 · 06-30-2015, 10:29 AM

in the /etc/passwd file for my user account I am set to tcsh.
so at the prompt if i do echo $SHELL i get /bin/tcsh.... obviously.

if i write a script that is:
#/bin/bash
echo $SHELL

it still responds with /bin/tcsh

is that normal?
is that a security feature?
what am i missing?
thanks.

netnix99 · 06-30-2015, 10:47 AM

It is perfectly normal. The correct way to write te first line is actually

Code:

#! /bin/bash

However, that still would not alter what was actually taking place here. All you would be doing is creating a script, telling the script to execute within the BASH shell, and then read your environment variable of $SHELL, which is STILL tcsh.

If you want to write a shell script that CHANGED your SHELL for the current terminal session ONLY, it would be:

Code:

#! /bin/bash

export SHELL=/bin/bash

Once you closed the terminal session you were in when this script was ran (or in any other terminal that you opened), your default SHELL will still be tcsh. If you want to alter your login shell to BASH, you need to edit the /etc/passwd file or change your .profile in your home directory to designate the change.

ron7000 · 06-30-2015, 11:53 AM

typo on my part missing the ! on the #/bin/bash when posting.

what i was overlooking was the echo $SHELL was being referenced from the user environment, not within the script.
thanks.

cfajohnson · 07-01-2015, 02:50 PM

The $SHELL variable only contains your default shell.

Running this script will not change the value of SHELL:

Code:

#! /bin/bash

export SHELL=/bin/bash

...unless you source it, in which case the shebang line is meaningless.