[Bug 1100775] [NEW] Man page incorrectly states that '-' must be last

[maf]

Public bug reported:

The manual page for su (shadow version 1:4.1.4.2+svn3283-3ubuntu7)
states:

       -, -l, --login
           Provide an environment similar to what the user would expect had
           the user logged in directly.

           When - is used, it must be specified as the last su option. The
           other forms (-l and --login) do not have this restriction.

The last paragraph here is wrong. The option '-' can be used anywhere on
the command line, as long as it comes before the name of the user you
want to su to.  So the only place it certainly doe snot work at is the
last position.

This can be tested fairly easily. On my system the user 'nobody' does not have a home directory, so su gives an error message when trying to create a login shell for nobody (running as root):
  # su nobody -c true
  # su nobody -c true -l 
  No directory, logging in with HOME=/

Using this we can eperiment where '-' works:
  # su - nobody -c true
  No directory, logging in with HOME=/
  # su nobody - -c true 
  # su nobody -c true -
  # su -c true - nobody
  No directory, logging in with HOME=/

Which gives that '-' only works when it comes before the username. This
is also obvious when one looks at the source. Let me know if I need to
elaborate on this.

** Affects: shadow (Ubuntu)
     Importance: Undecided
         Status: New

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https://bugs.launchpad.net/bugs/1100775

Title:
  Man page incorrectly states that '-' must be last

Status in “shadow” package in Ubuntu:
  New

Bug description:
  The manual page for su (shadow version 1:4.1.4.2+svn3283-3ubuntu7)
  states:

         -, -l, --login
             Provide an environment similar to what the user would expect had
             the user logged in directly.

             When - is used, it must be specified as the last su option. The
             other forms (-l and --login) do not have this restriction.

  The last paragraph here is wrong. The option '-' can be used anywhere
  on the command line, as long as it comes before the name of the user
  you want to su to.  So the only place it certainly doe snot work at is
  the last position.

  This can be tested fairly easily. On my system the user 'nobody' does not have a home directory, so su gives an error message when trying to create a login shell for nobody (running as root):
    # su nobody -c true
    # su nobody -c true -l 
    No directory, logging in with HOME=/

  Using this we can eperiment where '-' works:
    # su - nobody -c true
    No directory, logging in with HOME=/
    # su nobody - -c true 
    # su nobody -c true -
    # su -c true - nobody
    No directory, logging in with HOME=/

  Which gives that '-' only works when it comes before the username.
  This is also obvious when one looks at the source. Let me know if I
  need to elaborate on this.

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