While loop never ends

Question

I'm working with bash and I'm trying to do something like this:

A=1
while [ $A=1 ]; do
    read line
    echo $line | grep test >/dev/null   
    A=$?
    echo $A
done 

This script never ends even when the grep finishes successfully and A is set to 0. What am I missing here? Below is a sample of the output.

$ ./test.sh

asdf

1

test

0

hm...

1

Answer 1

You need to use the correct comparison operator. Bash has different operators for integer and string comparison.

In addition, you need the correct spacing in the comparison expression.

You need

while [ $A -eq 1 ]; do

See here for more

Answer 2

I find Bash's syntax pretty awful - have you tried something like:

while [ $A -eq 1 ] ... ?

It may be trying to re-assign 1 to $A or something strange like that.