UNIX for Dummies Questions & Answers

################################################################################################
#
#ACTION : 1) Search for the required attribute in the specified file and update if found.
#	  2) Add attribute on user's wish if not found in file.	
#DATE   : October 21, 2008	  
#AUTHOR : Himanshu Kansal
#NOTES	: Updates required attributes, also those with '/' as part of value such as path values.
#	: Uses '^' as sed operator instead of traditional '/'.
#
################################################################################################

#!/bin/sh

addAttribute(){
	file=$1
	attrib=$2
	value=$3
	
	while [ ! "$choice" = "y" ]&&[ ! "$choice" = "Y" ]&&[ ! "$choice" = "n" ]&&[ ! "$choice" = "N" ]
	do
		echo "Do you want to add the attribute? y/n \c"
		read choice
		case "$choice" in
		[nN])
			echo "No Changes made to "$file
			exit 0
			;;
	
		[yY])
			cp $file htmp.txt
			echo "$attrib"'= '"$value" >> htmp.txt
			;;
		*)
			echo "Invalid Input\n"
			;;
		esac
	done
}

file=$1         # The File to edit
attrib=$2       # The attribute to edit
value=$3        # New value

if [ $# -ne 3 ]              						# Check for all required parameters
then
        echo "USAGE : h_edit.sh <filename> <attribute> <value>"         # Show usage for missing parameters
elif [ ! -s "$file" ]; then                                             # Check if file exists
        echo "File "$file" not found"
else
        grep '^'"$attrib"'=' $file > htmp.txt                           # Check if attribute exists
        if [ ! -s htmp.txt ]; then
                 echo "Attribute not found"
		 addAttribute $file $attrib $value
        else                                                            # Else update old value
                 sed "s^$attrib= .*^$attrib= $value^g" $file > htmp.txt # Store result in htmp.txt                 
        fi
	
	echo "\n\nNew File :- \n\n"
	cat htmp.txt							# Display Changes
	
	choice=""	
	while [ ! "$choice" = "y" ]&&[ ! "$choice" = "Y" ]&&[ ! "$choice" = "n" ]&&[ ! "$choice" = "N" ]
	do		
		echo "\n\nDo you want to save the file? \c"
		read choice
		case "$choice" in
		[nN])		
			echo "No Changes made to "$file
			exit 0
			;;
		[yY])
			mv htmp.txt $file
			;;				
		*)
			echo "Invalid Input"
			;;
		esac
	done
	
fi