shell script - while loop with multiple conditions
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shell script - while loop with multiple conditions
Hi,
I'm sure this is possible as this is a very basic programming technique.
What I'm after is a while loop with multiple conditions - or (||) between the conditions.
Something like this:
while [[ "$value" != "val1" || "$value" != "val2" || "$value" != "val3" ]]
do
<your code goes here>
done
The above will do what you want, you need to use double square brackets instead of single brackets.
Are you aware that using OR's (||) and NOT's (!=) like this in a while loop could cause some problems getting out of the loop? An exit or break is needed.
i haven't tried it yet but I'm not aware of "problems" in getting out of the loop if I'll do it this way.
Will the loop continue even when none of the conditions is true? Is there a different way I can do it to avoid the problems?
Once you enter the loop, you cannot leave it if you depend on the content of the value variable (the while statement will always be true). This isn't a bad thing per se, it depends on what you want to do.
Without knowing what it is you are trying to do it's kinda hard to give advise on how to proceed. And like I stated before, it could be that this is the correct sollution to your problem.
Yes, break will do the trick.
What I'm trying to do is to read a value from the user but I want to restrict him to 3 values only.
So inside the loop i have the 3 values as i stated beore and inside the loop i have the read command
(read value).
I think what the OP is trying to do, is limit the user input to 3 "good" values.
ie: after the loop has exited value should be either val1, val2, or val3.
the user need to enter a value but he has to choose one out of three.
My loop will ensure that if he hasn't entered one of those three then he will have to try again and again until he will enter one of those three.
while [ "$value" != "val1" || "$value" != "val2" || "$value" != "val3" ]
do
read value
done
You can also use select, if the user has to choose between val1, val2 and val3
Code:
PS3="Choose your value : "
select value in val1 val2 val3; do
case $value in
val1) echo val1 selected; break;;
val2) echo val2 selected; break;;
val3) echo val3 selected; break;;
esac
done
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