Puppy Linux Discussion Forum

[une]

I want to teach myself shell scripting in BASH.
How do I find out which shell I am currently in (ASH or BASH) from the command line?
How do I swap shells?
What is the difference between ASH and BASH?
Are these the only two shells on Puppy LInux 2.13?
Is there a command that will list all available shells?

[Gn2]

These are all generic Linux queries - use GOOGLE !



echo $ SHELL

bash - ash - sh , etc etc etc

Yes

As default included, Only two in Puppy

[une]

I tried to change shell using
# chsh
but received the message
sh: chsh: command not found

why did this not work?

I also tried
# echo $SHELL
and was told
/bin/sh
so I guess the sh is default shell in use.

When I look at the contents of /bin I see ash and sh are shown in light blue text and bash in lime green text. What do these colour differences represent?

[trapster]

ash is a symlink to busybox
sh is a symlink to bash

[une]

Thanks. Does this mean symbolic links are shown in light blue text and actual applications shown in lime green text?
I don't know why chsh command did not work.

[rarsa]

[une]

Thanks for your detailed help. My understanding is minimal but I thought that every bash shell was the same, containing many commands and that every bash shell would have. When I type chsh at the command line on my Mandrake 10 Linux desktop system (using bash), the command is recognized. But on my Puppy system the same command is not found within bash. I now assume then that even within the same shell, the commands and functionality varies between systems as they may contain different versions of the same shell. Is this correct?

I don't particluarly want to change shell, but my experiments led to this discovery that does not make sense to me yet.

Is it also the case that sh and bash are different shells (but very similar) and that Puppy only has bash? Thus the symbolic link from sh to bash is present so that scripts that reference sh will work in Puppy's bash shell.

[Gn2]

"sh" Is not a distinct Linux shell variant - & in Puppy - is a symlink to Bash !
Google for different Linux shells available , how they vary.
Bash is the default Linux command parser - it is backwards compatible in most cases - NOT all

As was explained, (by default) inclusion in Puppy has limited ash and Bash CLI parameters.

Temp shelve interest in other shells -concentrate on learning Linux basics & as need dictates, time permits, how to script using Bash.

Puppy forum is for distribution specific variations.

The best way to learn is by backing up (running in RAM mode obviates most full_install_to_hard drive concerns)
Then experiment - asking should be considered - as a last resort when unable to find resources, documentations.

[MU]

ash is a small inbuilt shell of busybox.
Busybox is used when Puppy boots, it allows to keep the initial ramdisk small.
Busybox is a binary, that includes several commands, that else are only available as seperate programs.
But this small size has a price: not the full set of options of these programs are available.

So when Puppy booted, it additionally offers the bash, that is loaded from the big file pup_2xx.sfs.
Bash compatibility is required by several programs.

Other shells like ksh or csh have specialized capabilities like support for mathematic functions.
You will find those on universitary systems.
We had one program once, that required csh, so you can extract it from this archive:
http://dotpups.de/files/unsorted-not-packaged/bsd-csh.tgz

The original limited sh is used no longer, as GN2 said, it usually is just a symlink to one of the others like the Bash (Bourne again shell), that has become quasi standard in Linux, as it is part of the GNU Utilities from the Free Software Foundation.
The FSF has rewritten several Unix-tools under a free license.
What we commonly know as "GNU/Linux" usually is the Kernel (the "real" Linux) plus the GNU Utilities like bash.
Mark

[PaulBx1]

Mark, thanks for your very clear synopsis here. I have seen the situation with Puppy's shells described here and there before, but usually in an unsatisfactory way that raised even more questions.

[rarsa]

[une]

Thanks for such detailed responses. You have cleared up a lot of issues for me. It is much appreciated.

[Gn2]

Just a note RE the supplied link Alternate shells:
Please be aware command {chsh} is used to alter default O/System LOGIN shell

That may not be advisable > ESP in Puppy

[une]

So it seems that the command chsh executes an application (if that application has been installed on the system) that changes the shell. This command does not execute a function built into the shell itself, unlike commands such as rm and grep. Do I have this much correct?
Sorry for not being distro specific, but I figure I may as well finish this thing now.

[Flash]

No, don't stop now. This is a subject which has needed clarification for some time. I'm adding this thread to the Beginners sticky index, under Educational discussions. Thanks to everyone who contributed helpful explanations.