Re: suggestion for cygutils - usermod (was Re: howto change home path in /etc/passwd)

[Igor Pechtchanski <pechtcha at cs dot nyu dot edu>]

On Mon, 12 May 2003, Bernard Kash wrote:

> "Igor Pechtchanski" <pechtcha@cs.nyu.edu> wrote in message
> news:<Pine.GSO.4.44.0305121055540.393-100000@slinky.cs.nyu.edu>...
> > On Mon, 12 May 2003 Sylvain.Ferriol@imag.fr wrote:
> >
> > > Surlignage Max Bowsher <maxb@ukf.net>:
> > >
> > > > Sylvain.Ferriol@imag.fr wrote:
> > > > > Yes , because i don't want to create a shell doing this: grep -v
> > > > > $USERNAME /etc/passwd > /etc/passwd
> > > >
> > > sorry
> > > but i don't know with sed how to delete a line starting with $USER
> >
> > For the record: "sed '/'$USER':/d".  However, grep is perfectly
> > adequate.  What Max was warning you about was the shell redirection
> > mechanism.  You'd be safer using something like
> >
> >   cp -p /etc/passwd /etc/passwd-bak-tmp && grep -v $USERNAME > /etc/passwd-bak-tmp > /etc/passwd && rm -f /etc/passwd-bak-tmp
>
> Unfortunately, if you have a user named Homer that uses
> 'home' as his userid, the grep will eliminate more users
> than you might expect.  A more realistic example might be
> two users 'ted' and 'ed' when modifying user 'ed'.

Umm, yes, you're quite right.  I was addressing the redirection comment,
but should have noticed this as well.  Ok, here we go.  You can use either
of the below:

  (1) grep -v "^$USER:"
  (2) sed '/^'"$USER"':/d'
  (3) sed 's/^'"$USER"':.*$//'
  (4) awk -F: '$1!="'"$USER"'"{print}'
  (5) perl -pe 's/^'"$USER"':.*$//'
  ...

Well, you get the drift...  (1), (3), (4), and (5) can be used in a
case-insensitive manner (how is left as an exercise for the reader). ;-)
	Igor

> Also, the mkuser -p option expects a base directory,
> so if $HOME is "/home/usrname" the resulting record
> will set HOME to "/home/username/username"
>
> I've used awk delete a user from passwd...
>
> awk -F: -v usr=$USERNAME '{IGNORECASE=1; if($1 != usr) print $1;}'
> /etc/passwd
>
> BB
>
> > > > Care! That will leave you with an empty /etc/passwd.
> > > > The shell truncates /etc/passwd BEFORE grep reads it.
> > > >
> > > > > mkpasswd -l -u $USERNAME -p $HOME >> /etc/passwd

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