[devtac@test_1 shell]$ vi check_user.sh
#! /bin/sh
echo "You are logged in as `whoami`";
if [ `whoami` != devtac ]; then
  echo "Must be logged in as devtac to run this script."
  exit
fi
echo "Running script at `date`"

[devtac@test_1 shell]$ chmod a+x check_user.sh 
[devtac@test_1 shell]$ ./check_user.sh 
You are logged in as devtac
Running script at 2014年 12月 09日 星期二 13:35:17 CST

[devtac@test_1 shell]$ vi do_continue.sh
#! /bin/sh
doContinue=n
echo "Do you really want to continue? (y/n)"
read doContinue
if [ "$doContinue" != y ]; then
   echo "Quitting..."
   exit
fi
echo "OK... we will continue."

[devtac@test_1 shell]$ ./do_continue.sh 
Do you really want to continue? (y/n)
y
OK... we will continue.
[devtac@test_1 shell]$ ./do_continue.sh 
Do you really want to continue? (y/n)
n
Quitting...
[devtac@test_1 shell]$

[devtac@test_1 shell]$ vi hide_input.sh
#! /bin/sh
stty -echo
echo -n "Enter the database system password:"
read pw
stty echo

echo "$pw was entered"

 ./hide_input.sh 
Enter the database system password:123qweasd was entered
[devtac@test_1 shell]$

DESCRIPTION
Print or change terminal characteristics.

[devtac@test_1 shell]$ stty -a
speed 38400 baud; rows 47; columns 125; line = 0;
intr = ^C; quit = ^\; erase = ^?; kill = ^U; eof = ^D; eol = <undef>; eol2 = <undef>; swtch = <undef>; start = ^Q; stop = ^S;
susp = ^Z; rprnt = ^R; werase = ^W; lnext = ^V; flush = ^O; min = 1; time = 0;
-parenb -parodd cs8 -hupcl -cstopb cread -clocal -crtscts -cdtrdsr
-ignbrk -brkint -ignpar -parmrk -inpck -istrip -inlcr -igncr icrnl ixon -ixoff -iuclc -ixany -imaxbel -iutf8
opost -olcuc -ocrnl onlcr -onocr -onlret -ofill -ofdel nl0 cr0 tab0 bs0 vt0 ff0
isig icanon iexten echo echoe echok -echonl -noflsh -xcase -tostop -echoprt echoctl echoke