Question

I want to make a build chain script, and I don’t want it to perform until the end if there are error during compilation.

It’s the first time I write a more “elaborated” script in bash, and it just doesn’t work:

1. it doesn’t echo ERROR although I have lines with the word error in it
2. whatever the value of testError, the script just hangs in the line

this is the code:

testError=false

output=$(scons)
while read -r line; do
    if [[ $line == .*[eE]rror.* ]] ; then echo 'ERROR' ; $testError = true ; fi #$testError = true fi
done

echo $testError
if  $testError  ; then exit ; fi;

... other commands

EDIT: Following all posters answers and Bash setting a global variable inside a loop and retaining its value — Or process substituion for dummies and How do I use regular expressions in bash scripts?,
this is the final version of the code.
It works:

testError=false

shopt -s lastpipe
scons | while read -r line; do
  if [[ $line =~ .*[eE]rror.* ]] ; then
    echo -e 'ERROR' 
    testError=true 
  fi 
  echo -e '.'
done

if  $testError  ; then
    set -e 
fi

Answer 1

You set the value of testError in a subshell induced by your pipeline. When that subshell exits (at the end of the pipeline), any changes you made disappear. Try this:

while read -r line; do
   if [[ $line == .*[eE]rror.* ]] ; then
     echo -e 'ERROR' 
     testError=true 
   fi #$testError = true fi
done < <( scons )

or, if you don’t want or can’t use process substitution, use a temporary file

scons > tmp
while read -r line; do
  if [[ $line == .*[eE]rror.* ]] ; then
    echo -e 'ERROR' 
    testError=true 
  fi #$testError = true fi
done < tmp

This eliminates the pipeline, so the changes to testError persist after the while loop.

And, if your version of bash is new enough (4.2 or later), there is an option that allows the while loop at the end of a pipeline to execute in the current shell, not a subshell.

shopt -s lastpipe
scons | while read -r line; do
  if [[ $line == .*[eE]rror.* ]] ; then
    echo -e 'ERROR' 
    testError=true 
  fi #$testError = true fi
done