#!/bin/sh 
#
# This script gives the su command on HP/UX and SGI's a little sanity.
# To use this, alias su to 'alias su su root -c su-shell' .  It looks
# up the user in the password database (first checking netinfo root,
# netinfo local, /etc/passwd, or NIS) and extracts the login shell.
# If it is a valid shell (in /etc/shells) then it extracts the home
# directory, exports this as HOME, and runs the user's login shell.
#
# Eric Myers <myers@umich.edu>		: 27 October 1995
# Department of Physics, University of Michigan, Ann Arbor, MI
# @(#) $Revision: 1.4 $ - $Date: 1997/03/17 23:39:31 $  
#======================================================================*
PROG=`basename $0`
#PSAUX="ps -auxg"  # BSD
PSAUX="ps -ef"
LOGSHELL=""

if [ -z "$USER" ]; then
  echo "$PROG: USER: undefined variable."
  exit 3
fi


# -- NetInfo on a NeXT: look for password entry in / or . maps

if [ -x /usr/bin/nidump ]; then
  PASSWD="/usr/bin/nidump passwd / "
  LOGSHELL=`$PASSWD | awk -F: "\\\$1 ~ /^$USER$/ {print \\\$7}" `
  if [ -z "$LOGSHELL" ]; then
    PASSWD="/usr/bin/nidump passwd . "
    LOGSHELL=`$PASSWD | awk -F: "\\\$1 ~ /^$USER$/ {print \\\$7}" `
  fi
fi

# -- If no luck, try /etc/passwd

if [ -z "$LOGSHELL" ]; then
  PASSWD="cat /etc/passwd"
  LOGSHELL=`$PASSWD | awk -F : "\\\$1 ~ /^$USER$/ {print \\\$7}" `
fi

# -- If still nothing, and NIS is running (ypbind) also look in the YP
#    database 

if [ -z "$LOGSHELL" ]; then
  YP=`$PSAUX | grep ypbind | grep -v grep`
  if [ ! -z "$YP" ]; then 
    PASSWD="ypcat passwd"
  fi
  LOGSHELL=`$PASSWD | awk -F : "\\\$1 ~ /^$USER$/ {print \\\$7}" `
fi

# -- If nothing by now, give up

if [ -z "$LOGSHELL" ]; then
  echo "$PROG: no shell."
  exit 1		# no shell, so exit
fi

# -- For login shell to be valid it must be in /etc/shells

if [ -z "`grep $LOGSHELL /etc/shells`" ]; then
  echo "$PROG: $LOGSHELL: not a valid shell."
  exit 2		# not a valid shell
fi

# -- Get the home directory and export it to the subshell

HOME=`$PASSWD | awk -F: "\\\$1 ~ /^$USER$/ {print \\\$6}" `
export HOME

# -- Run the user's login shell

$LOGSHELL

exit