[ale] Bash scripting q

[J. D.]

On Thu, May 8, 2008 at 6:42 PM, JK <jknapka at kneuro.net> wrote:

> J. D. wrote:
> > Is the desired effect for it to expand to /home/callinguser/user?
>
> No, the desired effect is for it to expand to the home
> directory of the user name supplied to the script as
> arg $1.  So if I say:
>


Oh OK that makes sense. If root is running the script though, isn't the
tilde
most always going to return the home directory of the calling user root?

Using sudo to get the home directory of the target user might be an option.

USERHOME=`sudo -u joe pwd`



>
> ./myscript joe
> I need a way within myscript to refer to "joe"'s home, which on
> my system happens to be /home/joe.  I cannot make any such
> assumptions about the target system, though (that user home
> directories live under /home, I mean).  Which is why I
> want to use the tilde.
>
> -- JK
>
> > Usually the tilda should expand to /home/user right? I'm not sure why
> > you are using the tilda. $USER is a bash builtin but I guess there is no
> > harm in resetting it.
> >
> > for me this works:
> >
> > #!/bin/bash
> >
> > USER=$1
> > cp foo /home/$USER
> > chown $USER /home/$USER/foo
> >
> >
> > On Thu, May 8, 2008 at 3:38 PM, JK <jknapka at kneuro.net
> > <mailto:jknapka at kneuro.net>> wrote:
> >
> >     Hi folks,
> >
> >     I am trying to do a very simple thing, and getting screwed by bash's
> >     evaluation
> >     rules.  Basically, I need to write a script that accepts a user name,
> >     and then
> >     copies some files to that user's home dir, and also chowns them to
> that
> >     user.
> >     So I tried the obvious:
> >
> >     #!/bin/bash
> >     USER=$1
> >     cp foo  ~$USER
> >     chown $USER ~$USER/foo
> >
> >     This totally fails to work as I expect, because tilde expansion
> happens
> >     before variable expansion.  So if I supply 'joe' as the first arg,
> >     "~$USER"
> >     expands to ~joe (instead of the desired /home/joe), and the cp
> >     effectively
> >     evaluates to "cp foo '~joe'", which ends up creating a regular file
> >     named
> >     ./~joe
> >
> >     Is there a clean workaround?  I'd rather not force the user to
> >     supply both
> >     the user name and the user's home directory as script arguments.  And
> >     doing a grep'n'cut on /etc/passwd is not too appealing either.  I've
> >     checked
> >     a couple of books ("bash Cookbook", "Linux Shell Scripting", and an
> >     online tutorial or two), but the most any of them say is "Don't do
> >     that";
> >     they provide no workaround.
> >
> >     An explicit command to force shell expansion of an arbitrary string
> >     would
> >     do the trick... I'm goofing around with echo and eval right now, with
> >     interesting, but not useful, results...
> >
> >     Oops, just stumbled on an answer:
> >
> >      cp foo $(eval echo $(echo ~$USER))
> >
> >     works, although it makes my eyes water a bit.  Is there a better way?
> >     (This post has devolved to the "Linux trivia quiz" level...)
> >
> >     Thanks,
> >
> >     -- Joe
> >
> >     --
> >     I do not particularly want to go where the money is -
> >      it usually does not smell nice there. -- A. Stepanov
> >
> >
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> >
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> >
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>
> --
> I do not particularly want to go where the money is -
>  it usually does not smell nice there. -- A. Stepanov
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