Shell Programming and Scripting

#!/bin/sh
autodate=`date "+%Y%m%d"`
data1=$1
setdate=$2
if [ $data1 = $NULL ]; then
    echo "Usage - enter the data1 then the date in YYYYMMDD format"
    echo "Usage - You can also enter just the data1 to use autodates Date"
    echo "Example: sh $0 data $autodate"
    exit
fi
if [ $setdate = $NULL ]; then
    echo "Searching for data1: $data1 on date: $autodate"
    cd /dir/
    grep $data1 $autodate*.log
    echo Done searching
    cd /home/
    exit
fi
if [ $setdate != $NULL ]; then
    echo "Searching for data1: $data1 on date: $setdate"
    cd /dir/
    grep $data1 $setdate*.log
    echo Done searching
    cd /home/
    exit
fi

if [ ! -n $data1 ]; then

if [ -z $data1 ]; then

if [ $# -ne 2 ]; then
  echo Usage: $0 data1 setdate
  echo where setdate is in mm/dd/yyyy format
  exit 1
fi

 
if [ $# -eq 2 ]; then
  setdate=$2
  data1=$1
elif [ $# -eq 1 ]; then
  data1=$1
  ... derive setdate...
else
  echo usage: data1 '[setdate]'
  exit 1
fi