From colin!hphbbs.E.open.DE!hph Sat May 21 23:02:58 1994
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From:	hph@hphbbs.E.open.DE (H.P.Heidinger)
Subject: ttyenable/-disable V1.5
To:	oklein@smallo.BO.open.de (Olaf Klein),
	gert@greenie.muc.de (Gert Doering)
Date:	Sat, 21 May 1994 17:29:46 +0200
Reply-To: hph@hphbbs.E.open.DE
Organization: HPHBBS - UseNet City-Router, Essen (Germany)
Phone: +49-201-287433 (data+voice) Voice = 3 times 1 ring, wait on 4th call
X-Mailer: ELM [version 2.4 PL23]
Content-Type: text
Content-Length: 10697     
Status: RO

Hi,

   Anbei kommt ttyenable/-disable V1.5.
   Gegenueber V1.2 sind folgende Maengel behoben:

   	- ein Bug, nachdem zB ttyS2 und ttyS20..29 gleich handelt
	  wurden (in Funktion 'isTTY'):
	     
 	  alt:  gotcha=`find /dev -type c -follow|grep /dev/$token`	&&\
 	  neu:  gotcha=`find /dev -type c -follow|grep -w /dev/$token`	&&\

	  Hinweis: das "ange'pipe'te" grep ist absolut notwendig, weil
	  "find" leider IMMER einen Exit-Code von 0 (true) ausspuckt,
	   wenn er nicht SELBST aus irgendwelchen Gruenden kaputt geht.
	   Wenn "ls" nicht so eloquent waere, wenn das gesuchte Device
	   NICHT existiert ("No such blafasel ..."), wuerde sich das
	   zeitaufwendige "find|grep" auch ersetzen lassen.
	   Vorschlaege??

        - ein Crosscheck gegen die temporaere 'inittab', um mehrfache
	  gettys auf dem selben Device aber unter verschiedenen Labels
	  auszuschliessen (siehe Programmtext, Funktion: 'crosscheck'

--------------------------- 8< schnipp ... schnapp 8< --------------------------
#!/bin/sh 
#set -x
###############################################################################
# /etc/ttyenable (link to /etc/ttydisable as well)	-- for LINUX
# (C)May-1994, H.P. Heidinger, Essen, Germany -- All rights released!
# -----------------------------------------------------------------------------
# Rights: -rwx------   1 root     root            0 May 13 14:29 /etc/ttyenable
# -----------------------------------------------------------------------------
#   Enable/Disable tty channels in the inittab-file; i.e. change the
#   entry for a given device from :off: to :respawn: and vice-versa.
#
#   Usage: a){ttyenable|ttydisable} [-D] [ -v] [ -h] <spec>
# 	   b){ttyenable|ttydisable} [-D] [ -v] [ -h] { -d <device> | -l <label>}
#
#   Mode a) is auto-detection. The program checks itself whether <spec>
#   was a label in inittab or a device name.
#
#   Mode b) might be used in tough situations, where one needs to specify
#   explicitly whether a label or device is meant.
#
#   Options:
#	-h hangup init process
#	-v verbose on
#	-D debug on
# 	-d <device> 
#	-l <label>
#
#   Although mode b) is actually not needed it is supplied via commandline
#   options, since the corresponding modules are in this program.
#
########################### RCS stamps ########################################
# $Id: ttyenable,v 1.5 1994/05/21 14:49:50 root Exp root $
# $Log: ttyenable,v $
# Revision 1.5  1994/05/21  14:49:50  root
# some cosmetics at error reporting
#
# Revision 1.4  1994/05/15  19:59:57  root
# fixed a bug in device checking: e.g. ttyS2 and ttyS2? were treated even
#
# Revision 1.3  1994/05/15  16:01:31  root
# added device checking
# added crosschecking for multiple gettys on the same device
# ... with different labels
#
# Revision 1.2  1994/05/14  12:30:50  root
# added auto-determination (device or label)
#
# Revision 1.1  1994/05/13  18:23:13  root
# Initial revision
#
#
###############################################################################

#################################
#	Constants
#################################
InitTab=/etc/inittab
LockDir=/usr/spool/uucp
TTYmajors="4 5"

DEBUG=0
VERBOSE=0

###################################
#	Globals
###################################
Entry=''
Linenum=''
Label=''
Device=''
Major=''
Minor=''

trap cleanup 0

#################################
#	Functions
#################################
cleanup()	{ rm -f $InitTab.tmp }
handlerrors()	{ echo "$Linenum"; exit 1 }
fatal()		{ echo "$0: PROGRAM ERROR: $1 .. exiting"; exit 1 }
die()		{ echo "$0: Nothing appropriate $*"; exit -1 }

view()		{ echo "$*" >/dev/tty }

##+
# Look up a token in /dev; 
# If found clarify whether it is:
#   - a character device ... AND ...
#   - a tty (system-specific, [see 'TTYmajors' above])
#
# We return 'true' (0) to indicate that the device exists (by name, sym-links
# are followed) and IS a tty -- otherwise we point out 'false' (1)
#
##-
isTTY() {
local token=$1
local gotcha=''
local major=''
local minor=''
local i

	gotcha=`find /dev -type c -follow|grep -w /dev/$token`	&&\
	major=`ls -lL $gotcha |awk '{print $5}'|cut -f1 -d","`	&&\
	minor=`ls -lL $gotcha |awk '{print $6}'`

	if [ -z $gotcha ] 
	then return 1
	else	
		for i in $TTYmajors
		do
		   if [ .$major = .$i ]
		   then
			Major=$major
			Minor=$minor
			Device=$token

		        if [ $VERBOSE = 1  -o  $DEBUG = 1 ] 
		        then
		            view "Found device '$Device' ($Major,$Minor)"
		        fi
			return 0
		   fi
		done
	fi
	return 1
}


##+
# Determine the device associated with a label (found in field 4 of inittab)
# The major/minor-combo identifies the device definitely
#
# On entry we have a bare label.
#
# On exit we flag OK (return 0) and have set $Major/$Minor (global) by 'isTTY'
# Further we know the unique line number (global) in inittab and grabbed 
# that entry (global) for further investigations.
#
# Otherwise we give notice to die ... i.e. return 1 ... nah! we just die
##-
scandevice() {
local tokenlist
local i

	Linenum=`lookup_lab $1` 
	case $Linenum in
		ERROR*)	return 1
		;;
		[1-9]*) Entry=`sed -ne $Linenum\p $InitTab` \
			&& tokenlist=`echo $Entry | awk -F":" '{print $4}'`
		;;
		*)	die 
	esac
	
	if [ $DEBUG = 1 ]
	then
		view Line: $Linenum '=' $Entry
		view Tokenlist: $tokenlist
	fi

	###
	# Run over all tokens in field 4 and determine the device
	###
	for i in $tokenlist
	do
		if [ $DEBUG = 1 ]; then view "Dev-check $i";fi
		
		if isTTY $i
		then return
		fi
	done
	
	# Should never be reached
 	# bad times for liers ... empty tokenlist :-))
	die ": no associated device determined for $Label"
}


##+
# We have to take care that we never activate 2 gettys for the same device.
# This might easily be done, if we access the entry via a label; e.g.:
#
#	f1:2345:respawn:/etc/getty 19200 modem
#	v1:2345:off:/usr/local/etc/vgetty -s 38400 modem
#
# A simple 'ttyenable v1' would do the trick ... which we avoid here.
##-
crosscheck() {
local regex=".*:respawn:.*getty.*$Device"
local unique

	unique=`egrep -v "^[ \t]*\#" $InitTab.tmp | egrep -c "$regex"`

	if [ $unique != 1 ]
	then
	    view "FATAL: Would produce multiple gettys on device /dev/$Device"
	    view "`egrep -v "^[ \t]*\#" $InitTab.tmp | egrep "$regex"`"
	    die ": switch off other devices first"
	fi
}

##+
# Return a unique line number in inittab or flag "ERROR..."
##-
lookup_dev() {
	awk -F":" -v whichdevice=$1 '
	BEGIN { count=0 }
	/^[ \t]*\#/	{ next } # ignore comment lines
	/^[ \t]*$/	{ next } # ... and empty lines too
			{ if (index($4, whichdevice) != 0) { ++count; linum=NR } }
	END { if (count == 1) 
	           print linum
	      else if (count < 1)
			print "ERROR: not found ",whichdevice
		   else print "ERROR: ambiguous ",whichdevice,count,"times"  
	}
	' $InitTab
}

##+
# Return a unique line number in inittab or flag "ERROR..."
#
# Note that a LABEL in inittab can only exist once or init would complain
# ... makes it easier here
##-
lookup_lab() {
	awk -F":" -v whichlabel=$1 '
	BEGIN { count=0 }
	/^[ \t]*\#/	{ next } # ignore comment lines
	/^[ \t]*$/	{ next } # ... and empty lines too
			{ if (index($1, whichlabel) == 1) { ++count; linum=NR } }
	END {	if (count == 1) 
		     print linum
		else print "ERROR: no such Label",whichlabel
	}
	' $InitTab
}

lookup() {
	case $Mode in
		DEV)	 echo `lookup_dev $1` ;;
		LAB)	 echo `lookup_lab $1` ;;
	esac
}

log() {  
     case $0 in
     	*ttyenable)	TAG="to on"	;;
     	*ttydisable)	TAG="to off"	;;
     esac

     case $Mode in
	  DEV) logger "Changed (ge)tty state for device: \"$Device\" $TAG" ;;
	  LAB) logger "Changed (ge)tty state for label: \"$Label\" $TAG"  ;;
     esac
}

seton() {
	eval sed  -e "$Linenum\s/:off:/:respawn:/" $InitTab >$InitTab.tmp  \
	&& crosscheck \
	&& (mv $InitTab.tmp $InitTab; log)
}



setoff() {
	eval sed -e "$Linenum\s/:respawn:/:off:/" $InitTab >$InitTab.tmp \
	&& ( mv $InitTab.tmp $InitTab; log)
}

change() {
	case $0 in
	     *ttyenable)	seton	;;
	     *ttydisable)	setoff	;;
	esac
}

usage() { echo $0 '[ -D][ -h][ -v] { -d <device> | -l <label> | spec }' }


##################################################################
#
#	 Main program
#
##################################################################
while getopts "Dvhd:l:" arg
do
	case $arg in
	    D)  DEBUG=1		;;
	    v)  VERBOSE=1	;;
	    h)	HANGUPINIT=1	;;
	    d)	Device=`echo "$OPTARG"`;	Mode="DEV" ;;
	    l)	Label=`echo "$OPTARG"`;		Mode="LAB" ;;
	    ?)	usage; exit ;;
	esac
done

if [ "$OPTIND" -gt 1 ] ; then shift $[$OPTIND - 1]; fi


if [ .$Mode = "." ]
then
	if [ $# = 0 ]; then usage; exit; fi
	
	if egrep -q "^$1\:" $InitTab
	then
		Mode=LAB
		Label=$1
	else
		Mode=DEV
		Device=$1
	fi
fi


#######################################################################
# 1st step: no-one except root can do
# (although above rights should be set propperly and thus do the job)
#######################################################################

	if [ $LOGNAME != root ]
	then
		echo "$0: Sorry, only 'root' can do .. bye"
		exit
	fi

##########################################################
# 2nd step: get an unambiguous line from the inittab-file
##########################################################

	###
	# Check the junk which the user hacked in ...
	###
	case $Mode in
	     DEV) isTTY		$Device	&& Linenum=`lookup $Device` ;;
	     LAB) scandevice	$Label	;; # Linenum will be set by scandevice
	     *)	  fatal "no mode"
	esac

	###
	# Either we have now a number in 'Linenum' which designates the line
	# where the entry in inittab was found or the string "ERROR..."
	# In the latter case we can't go on.
	###
	case $Linenum in
		ERROR*)	handlerrors ;;
		[1-9]*)	change 
			######################################################
			# If we reach here everything went fine
			# So if the user requested to restart 'init' do so ...
			######################################################
			if [ .$HANGUPINIT != "." ]; then init Q; fi
		;;
		*)	die ;;	# Oh, well ....
	esac

# well ... done! welldone?
exit 0
--------------------------- 8< schnipp ... schnapp 8< --------------------------


    Kritik ist willkommen ...

Gruss, Peter	
-- 
####################===============================****************************
# H.P. Heidinger   # Call  : +49-201-287433 (data) *      ~~ HPHBBS  ~~       *
# Steeler Str. 121 #       : V22/32/42bis/FAX, 8N1 *    UseNet City-Router    *
# 45138 Essen      # E-Mail: hph@hphbbs.E.open.de  *    for Essen/Germany     *
# Germany          # Login : guest, gast, public   * anon. UUCP nuucp/nuucp   *
####################===============================****************************
# A supercomputer is a machine, that runs an endless loop in just 2 seconds   #