# File: /u/kscott/www/sysadmin/tools.notes
# Author: K. Scott Rowe
# Time-stamp: <02/01/2000 00:48:50 kscott@bendenweir.nmt.edu>


why not create a script called test?
  /bin/test

why use comments?
  someone else may have to change your scripts
  you may not know what you meant 6 months from now

how do rc startup scripts work?
  init is the first process run.  It runs the appropriate rc scripts
  (Single, Multi, 0, 1, 2, 3, ...)
  BSD usually only has two runlevels, Single and Multi user
  
    Slackware-Linux
      init calls inittab (Slackware-Linux)
      inittab calls rc.S (Slackware-Linux)
      This first rc file, does things like fsck, mount, swapon
      Then rc.M is run for all multi-user runlevels (2345)

    SunOS 4.x
      init calls rc.boot (SunOS)
      This first rc file, does things like fsck, mount, swapon
      Then either rc.single or rc.local is called
      

  SYSV usually has 8 0-6 and S
    init calls inittab
    inittab calls rc.sysinit (RedHat-Linux) or rcS (Solaris)
    This first rc file, does things like fsck, mount, swapon
    Then the run levels are run sequentially (rc0, rc1, rc2, rc3 (solaris))
    (rc 0, rc 1, ... (redhat))
if [ -d /etc/rc0.d ]; then
        for f in /etc/rc0.d/K*; do
                if [ -s $f ]; then
                        case $f in
                                *.sh)   .        $f ;;
                                *)      /sbin/sh $f stop ;;
                        esac
                fi
        done

        # System cleanup functions ONLY (things that end fast!) 

        for f in /etc/rc0.d/S*; do
                if [ -s $f ]; then
                        case $f in
                                *.sh)   .        $f ;;
                                *)      /sbin/sh $f start ;;
                        esac
                fi
        done
fi


#!/bin/sh
#
#Select a unique UID to assign a new user.  UID's selected are always >= 100
#
sort -t: +2n -3 "$1" | awk -F: 'BEGIN { u = 100; }
	                $3 == u { u++; next; }
        	        $3 > u  { print u; exit; }
	                                { next; }';

#
# or ...
#
x=100
while [ $x -lt 65535 ] ; do
    grep "^[^:]*:[^:]*:$x:.*$" /etc/passwd > /dev/null 2>&1
    if [ "$?" = "1" ] ; then
        echo "$x"
        exit
    fi
    x=`expr ${x} + 1`
done

echo "drat, ran out of numbers"