Why variable values are lost after terminating the loop in bash? [duplicate]

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This is BashFAQ #24. Fortunately, you’re only hitting it here because of an unnecessary use of cat — you have no good reason to have a pipeline in use at all.

The right-hand side of a pipeline (like the rest of its contents, being made up of transient subshells) exits when the pipe is done unless you have shopt -s lastpipe active.

Instead, either add the line:

shopt -s lastpipe

or restructure your loop:

while read LINE; 
do
      COUNT=`echo $LINE| awk '{print $2;}'`;
      TOTAL=$((TOTAL+COUNT));
done <"$DATAFILE"

…or, in a case where you really need to pipe from another process, use process substitution:

while read LINE; 
do
      COUNT=`echo $LINE| awk '{print $2;}'`;
      TOTAL=$((TOTAL+COUNT));
done < <(cat "$DATAFILE")

By the way, if your shebang is #!/bin/bash, not #!/bin/sh, this would be better written as follows:

total=0
while read -r _ count do; 
  (( total += count ))
done <"$DATAFILE"

read can split lines on characters in IFS itself — you don’t need to use awk for that.

By convention, variable names should be all-lowercase unless they represent environment variables or shell builtins.

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