скрипт отключения 3g модема

#!/bin/sh

killall pppd
sleep 3

cat /dev/ttyUSB0 &
x=$!
kill $x
sleep 3

exec /usr/sbin/chat -V -s -S                                    \
	ABORT		"BUSY"					\
	ABORT		"ERROR"					\
	ABORT		"NO DIALTONE"				\
	SAY		"\nSending break to the modem\n"	\
	""		"\K"					\
	""		"+++ATH"				\
	SAY		"\nPDP context detached\n"              \
	""              "AT+CFUN=1,1"                           \
	""              "ATZ"	                                \
        SAY             "OK"                                    
exit          

linux-bst0:~ # killall pppd
pppd: no process found
linux-bst0:~ # sleep 3
linux-bst0:~ # 
linux-bst0:~ # cat /dev/ttyUSB0 &
[1] 12469
linux-bst0:~ # x=$!
linux-bst0:~ # kill $x
linux-bst0:~ # sleep 3
[1]+  Terminated              cat /dev/ttyUSB0
linux-bst0:~ # 
linux-bst0:~ # exec /usr/sbin/chat -V -s -S                                    \
> ABORT"BUSY"\
> ABORT"ERROR"\
> ABORT"NO DIALTONE"\
> SAY"\nSending break to the modem\n"\
> \"\""\K"\
> \"\""+++ATH"\
> SAY"\nPDP context detached\n"              \
> ""              "AT+CFUN=1,1"                           \
> ""              "ATZ"                                \
>         SAY             "OK"                                   
exit