Using loops in a Search

gregarion · 01-21-2010, 08:08 AM

Code:

Title=
echo -n "Title: "
read Title
echo -n "Author:"
read Author




validation=`grep -i "$Title" fruit | grep -i "$Author"  | awk -F":" '{ print $1}'`


if [ "$Title" = "$validation" ] ; then
clear

echo "Error! Book Already Exist"

else
echo "You may input a new book in/

hey guys, im doing a simple search program and i came up with a problem. What i am trying to achieve is, if the search is false(means the book does exist) , the program will then ask the user to input the information again(title and author) and do a search again until there is no such book and then display a message saying he can input a new book in.

i tried using a until loop, but it does not seem to work. some guidance on how the statement should be and where should it be placed?

quanta · 01-21-2010, 09:20 AM

You can use "while [ 1 ]" and "break" like that:

Code:

#!/bin/sh
while [ true ] 
do
	echo -n "Please enter the first number: "
	read first
	echo -n "Please enter the second number: "
	read second
	if [ "$first" -ne "$second" ]; then
		echo "The first number is different from the second number. Please try again!"
	else
		echo "Congratulation! The first number is equal to the second number."
		break
	fi
done
exit 0

gregarion · 01-21-2010, 09:26 AM

Hey thank guanta, just to check, the "break" commands basically stops the loop from running again right? so basically if the numbers does equal, then the while command will read break which means it is true?

chrism01 · 01-22-2010, 01:34 AM

Quote:

break [n]
Exit from within a for, while, until, or select loop. If n is specified, break n levels. n must be >= 1. If n is greater than the number of enclosing loops, all enclosing loops are exited. The return value is 0 unless the shell is not executing a loop when break is executed.

http://linux.die.net/man/1/bash

grail · 01-25-2010, 02:31 AM

Just a side note on using break, as it is able to break out from any level of nested loops depending
on the number supplied, it can potentially make it very difficult to follow your code.

An alternative is to set a variable within your loop and test it to see what the value is:

ie. while [[ "x$TEST" != "xend" ]]
do
. . .
if [[ true_expression ]]
then
...
else
...
TEST=end
fi
done