While loop in shell script says [: too many arguments

Question

I'm trying to run a very simple script that reads input from a user and continuously loop a question if the users input doesn't match what is expected.

It's being execute via bash:

echo "Specify a directory [Y/N]?"

read ans
while [ [ "$ans" != "Y" ] || [ "$ans" != "y" ] || [ "$ans" != "N" ] || [ "$ans" != "n" ] ]
do
    echo "$ans is not valid, please answer [Y/N]"
    read ans
done

code continues....

Any idea why this is not working? It seems like a pretty straight forward loop.

To add to @chepner's comment - if you really do need grouping (in this case you don't - see Clement Rey's answer below), you need to use ( and ) instead (possibly with appropriate escaping/quoting, depending on your exact syntax). — twalberg
– twalberg, Commented Apr 1, 2013 at 17:50

cmc · Accepted Answer · 2013-04-01 17:50:27Z

1

That should work:

echo "Specify a directory [Y/N]?" 
read ans 
while [ "$ans" != "Y" ] && [ "$ans" != "y" ] && [ "$ans" != "N" ] && [ "$ans" != "n" ]
do
    echo "$ans is not valid, please answer [Y/N]"
    read ans 
done

There were a few mistakes:

you were probably thinking AND instead of OR
there is no global [ ] for a multiconditionnal while loop

edited Apr 1, 2013 at 17:50

answered Apr 1, 2013 at 17:45

cmc

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3 Comments

nullByteMe Over a year ago

That allows my program to proceed without the endless loop but I still get the "[: too many arguments" error. "

chepner Over a year ago

&& is the correct operator to use here, as $ans will always be unequal to one of the choices.

cmc Over a year ago

With ||, he is going in no matter what so I guess he wanted a &&.

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