Shell Scripting

What does #!/usr/bin/ksh means in shell scripting?

 It  is the first line in a shell script always

it signals os that the script is to be executed by ksh (instead of any of the other shells)

 shebang is the character sequence consisting of the characters number sign and exclamation mark (#!)

What do $? $0 $1 $2 mean in shell script?

These are positional arguments of the script.

  clone_dbapps.sh OSPT APPSONLY NOCOPY_APPSBIN   ( here $0 – clone_dbapps.sh, $1 – OSPT and so on )

 If parameter to clone_dbapps.sh is less than 1 then it would ask Usage

 test is an program which lets you perform various tests

Executing:

if test $# -lt  1

then

   echo

   echo

   echo " Usage:   $0  SID APPSONLY(optional) NOCOPY_APPSBIN(optional)"

   echo

   exit 9

fi

Whats the use of awk and substrr ?

   substr(s, a, b) : it returns b number of chars from string s, starting at position a. The parameter b is optional.

   Awk prints the output .

   export I=`echo $1|awk '{ print substr($1,1,1)}'`

   clone_dbapps.sh OSPT will return O