How do I update a "global" variable inside a while loop?

Question

So I have this If statement that checks what the exit code of the script is:

if [ $? -eq 0 ]; then
    wasSuccessful=true;
fi

In other languages, I would do something like:

while wasSuccessful == false

And then the loop would keep running until the exit code was true. (I plan to implement a loop counter as well for too many failed attempts, but that's a different problem to solve)

I think I need a here-string, but I'm not exactly sure how that would look. Here's a rough outline of my code right now, in Bash:

wasSuccessful=false

while [ "$wasSuccessful" = "false" ]
do

#Bunch of code here, then the check for exit code

if [ $? -eq 0 ]; then
    wasSuccessful=true;
fi

done

Any suggestions on how to do something like this would be much appreciated :)

Your code seems OK. What is the problem you are facing? All variables in Bash are global unless declared as local inside a function. — codeforester
– codeforester, Commented Jun 13, 2017 at 23:47
I thought the while loop executed in a subshell, so changes I make to variables are saved only to that session scope. Is that not correct? — iMatthewCM
– iMatthewCM, Commented Jun 13, 2017 at 23:54
@iMatthewCM the while loop not executed in subshell, unless you put them inside quote (commands). — alijandro
– alijandro, Commented Jun 13, 2017 at 23:55
The confusion is probably that often people will pipe input into a while loop, and things involved in a pipeline are run in subshells. So if you did, say, getent passwd user_prefix | while read -r ent; do... then that loop would be in a subshell, as written yours would not create a subshell — Eric Renouf
– Eric Renouf, Commented Jun 14, 2017 at 0:23

alijandro · Accepted Answer · 2017-06-13 23:54:35Z

2

The question is how to exit while loop when the latest command execute successfully inside while loop?

You don't need a global variable to check. Just check the status of previous command and break it if succeed.

while true
do
    # a bunch of code here
    [ $? -eq 0 ] && break
done

answered Jun 13, 2017 at 23:54

alijandro

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3 Comments

iMatthewCM Over a year ago

The opposite of that I think. If the exit code is anything other than 0, I need to keep looping.

alijandro Over a year ago

Yes, the code above will keep your loop running if the exit code is not 0.

iMatthewCM Over a year ago

Well...that's pretty awesome. Thank you very much! That's much more elegant than what I was doing. I'll give that a shot when I get back to work tomorrow (just leaving now) and if it works I'll accept the answer :)

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