Shell Programming and Scripting

Hi there,

And happy new year to everyone.
I was wondering how is set the default shell for executing scripts.
I mean when the first line of a script file is not

Code:

#!/bin/bash

Then what shell will be used to execute the script?
I thought the script file would be parsed using the current shell but the following shows that this is not the case:

Code:

santiago@ks354286:~$ readlink /proc/$$/exe # I'm currently using bash
/bin/bash
santiago@ks354286:~$ tcsh # I go into tcsh
ks354286:~> cat /tmp/test
readlink /proc/$$/exe
ks354286:~> /tmp/test
/bin/bash

Why would bash be used to run the script if my current shell is tcsh?

Can anyone help me?
Thanks in advance.

Santiago

Probably because you invoked tcsh from within bash.

Try logging in as a user with /bin/tcsh as their default and see what you get.

Hi Beaknit,

And thanks for helping.
I just changed my default shell to /usr/bin/tcsh in /etc/passwd and logged in again.
The defauly shell used to run the scripts is still /bin/bash.

Any other idea ?
Santiago

Distro, version, uname, etc

And can you post the script?

Also - sanity check: are you running it under cron?

depending on your default SHELL and how your system is setup, some config file may run as well (.bashrc in bash, .kshrc , .login, $HOME/.profile , /etc/profile, .... and so on).

they may change things.

you should logon with the shell that is defined in the /etc/passwd but if that shell run some environment file, those can change things (depending on what is setup into it).

when you are in bash,

instead of running

Code:

tcsh

try running :

Code:

exec tcsh

Do you see the difference ?

(in the first case it will make tcsh be a subprocess of the initial bash process, check it with ptree $$ or pstree $$ depending on your OS in the other case, it will make it the initial process)

This might not be true, or appliable to other Unices, but I think the default shell for scripts in Linux is /bin/sh, which is usually just a copy of or link to /bin/bash.

What is the output from:

Code:

ls -lisad /usr/bin/tcsh
ls -lisad /usr/bin/bash