bash - A variable modified inside a while loop is not remembered -

in following program, if set variable $foo value 1 inside first if statement, works in sense value remembered after if statement. however, when set same variable value 2 inside if inside while statement, it's forgotten after while loop. it's behaving i'm using sort of copy of variable $foo inside while loop , modifying particular copy. here's complete test program:

#!/bin/bash  set -e set -u  foo=0 bar="hello"   if [[ "$bar" == "hello" ]]     foo=1     echo "setting \$foo 1: $foo" fi  echo "variable \$foo after if statement: $foo"    lines="first line\nsecond line\nthird line"  echo -e $lines | while read line     if [[ "$line" == "second line" ]]         foo=2     echo "variable \$foo updated $foo inside if inside while loop"     fi     echo "value of \$foo in while loop body: $foo" done  echo "variable \$foo after while loop: $foo"  # output: # $ ./testbash.sh # setting $foo 1: 1 # variable $foo after if statement: 1 # value of $foo in while loop body: 1 # variable $foo updated 2 inside if inside while loop # value of $foo in while loop body: 2 # value of $foo in while loop body: 2 # variable $foo after while loop: 1  # bash --version # gnu bash, version 4.1.10(4)-release (i686-pc-cygwin) 

echo -e $lines | while read line  ... done 

the while loop executed in subshell. changes variable not available once subshell exits.

instead can use here string re-write while loop in main shell process; echo -e $lines run in subshell:

while read line     if [[ "$line" == "second line" ]]         foo=2     echo "variable \$foo updated $foo inside if inside while loop"     fi     echo "value of \$foo in while loop body: $foo" done <<< "$(echo -e "$lines")"