Incrementing a variable inside a Bash loop

Question

I\'m trying to write a small script that will count entries in a log file, and I\'m incrementing a variable (USCOUNTER) which I\'m trying to use after the loop

Answer 1

• Always use -r with read.
• There is no need to use cut, you can stick with pure bash solutions.
  • In this case passing read a 2nd var (_) to catch the additional "fields"
• Prefer [[ ]] over [ ].
• Use arithmetic expressions.
• Do not forget to quote variables! Link includes other pitfalls as well

while read -r country _; do
  if [[ $country = 'US' ]]; then
    ((USCOUNTER++))
    echo "US counter $USCOUNTER"
  fi
done < "$FILE"

Answer 2

I had the same $count variable in a while loop getting lost issue.

@fedorqui's answer (and a few others) are accurate answers to the actual question: the sub-shell is indeed the problem.

But it lead me to another issue: I wasn't piping a file content... but the output of a series of pipes & greps...

my erroring sample code:

count=0
cat /etc/hosts | head | while read line; do
  ((count++))
  echo $count $line
done
echo $count

and my fix thanks to the help of this thread and the process substitution:

count=0
while IFS= read -r line; do
  ((count++))
  echo "$count $line"
done < <(cat /etc/hosts | head)
echo "$count"