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while - loop does not work

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Top Forums Shell Programming and Scripting while - loop does not work
# 1  
Old 03-24-2010
Tools while - loop does not work
Hey guys,

maybe you can help me.. what am i doing wrong?
Why this doesn`t work in ksh.

Code:
        while [ "${decision}" != "y"  ||  "${decision}" != "n" ]
        do
        echo "Type y or n"
        read decision
                if [ "${decision}" = "y" ]
                then
                doInstall
                fi
        done

i also tried this

Code:
        while [ "${decision}" != "y" ] || [ "${decision}" != "n" ]
        do
        echo "Type y or n"
        read decision
                if [ "${decision}" = "y" ]
                then
                doInstall
                fi
        done

I want the loop to be endet as soon as the user types in y or n.
But it just doesnt end.

Thanks a lot in advance.

Regards
xcitan
# 2  
Old 03-24-2010
Code:
#!/bin/ksh
while true
        do
        echo "Type y or n"
        read decision
                if [[ "${decision}" = "y" ]]
                then
                  echo doInstall
                else
                  exit
                fi
        done

# 3  
Old 03-24-2010
try with the following
Code:
        while [ "${decision}" != "y"  -o  "${decision}" != "n" ]
        do
        echo "Type y or n"
        read decision
                if [ "${decision}" = "y" ]
                then
                echo "execute it"
                                exit 0
                                else
                                        continue
                fi
        done

# 4  
Old 03-24-2010
hi malcom,

thank you for your answer, but that is not what i am looking for.
May you tell me if something like this works in a while loop?
Code:
while [ "${decision}" != "y" ] || [ "${decision}" != "n" ]

Regards
xcitan
# 5  
Old 03-24-2010
Quote:
Originally Posted by xcitan
hi malcom,

thank you for your answer, but that is not what i am looking for.
May you tell me if something like this works in a while loop?
Code:
while [ "${decision}" != "y" ] || [ "${decision}" != "n" ]

Regards
xcitan
check what expert suggested you above.
# 6  
Old 03-24-2010
Hi Expert,

am i right, that -o means or?!

Code:
  while [ "${decision}" != "y"  -o  "${decision}" != "n" ]

I dont know why, but although i type in y or n the while loop doesn`t end. *grml*
I even check for it and i can see that
Code:
${decision}

is y or n.

Thanks for your help.
xcitan
# 7  
Old 03-24-2010
ofcourse, the while loop will not end because it always return true.
Assume, you entered "n" after it asks you to type y or n.
Then it compares that if decision is not "y", it returns true because decision is "n"(not y) and it checks the next one if decision is not "n", it returns false because it is "n". So either way, you entered y or n, it returns true because

Quote:
True OR True = True
True OR False = True
False OR True = True
False OR False = False
i hope you get what i mean.
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