You can happily have more than one shell installed and decide on a per-user basis which one to use.


A better place for this would be your signature.

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All shell programs are Command and Programming Languages -- from sh to ksh to base, that's what they are: you execute commands and you can write useful programs in the shell. That would also include derivatives of C-Shell (which is NOT the same thing as Bourne, Korn or BASH, it came out of Berkeley and is distinctive by its convoluted grammar and syntax).

BASH (Bourne Again Shell) is a combination of sh and ksh (the functionality, not the underlying code) with some "extensions" and "features" thrown in. Generally, BASH will run sh and ksh code without too much arguing -- not everything, but pretty much. The grammar and syntax of BASH and KornShell are close enough that you program in the one and run in the other if you're not using BASH extensions (which neither Bourne or KornShell have).

As to user shell preference, it is quite simple to change the 7th field of the user entry in /etc/passwd (optional user command interpreter). This can be done by direct edit of the file (as root) or with usermod -s /bin/shell_name USERNAME (also as root).

A typical user account line looks like this:
In the example the optional user command interpreter is KornShell. That could be changed to BASH with
It could also be changed to lock out any log in with
You may have noticed if you've looked at /etc/passwd that all of the administrative accounts (except root listed are /bin/false; i.e., you cannot log in to those accounts (attempts will result in immediate exit).

So, anyway, shells are pretty much command interpreters that let you execute commands and write useful programs.

Hope this helps some.

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Two good points, thank you.

If I get to play around enough with zsh on the RasPi to become proficient, I'll change my login shell on the Slackware box per tronayne's information (but not until then <grin>).

Signature enabled, per your suggestion.

Thankx again to both of you.

Well, you can't su to a user with /bin/false, or yes, technically you can, but the user's shell starts, and if it's /bin/false, exits immediately ( without reading a single command from the terminal )...
Normally the user's shell should listed in /etc/shells, that is checked by the pam_shells module, but the /bin/false exits right after the invocation so that is not too usuable.

Oh, an by the way, if it's allowed, a user can change hisown shell with the chsh command.

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Oops! Yes, /bin/false exits immediately, duh. A little confused about admin accounts where there is a shell specified (when I've been naughty and done such a silly thing).

About PAM. PAM is not installed by default on Slackware systems -- it's available if needed at Slackbuilds.org but its use is discouraged unless absolutely, positively you must have it for something or other..

Thanks for the reminder.

Do you know the reason for this attitude?

A lot of reasons, actually. There is a current thread about PAM and Slackware you may find interesting, a particular post being http://www.linuxquestions.org/questi...ml#post5205085 although the entire thread may be of interest.

Hope this helps some.

Ah, okay, thank you. I was just wondering, since SuSE uses PAM since -- oh, probably the glaciers were still around or so .

Make sure the blackslash character is the last character on the line before the <lf>. It is an escape character.

This line "this is a single line \A" will output the line "this is a single line A".

This "some shell command line \ <lf>" will result in the space character after the backslash being kept and the newline will be treated as the end of the line. The line output would be "some shell command line <lf>".

For the line to be continued you need to ensure it is "text of the line \<newline>". And if the shell script line ends with "\<cr><lf>" it might cause a problem as well.

Any time I run into this problem I immediately check for trailing space characters and I inevitable find one or more.