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In the following program, if I set the variable $foo to the value 1 inside the first if statement, it works in the sense that its value is remembered after the if statement. However, when I set the same variable to the value 2 inside an if which is inside a while statement, it's forgotten after the while loop. It's behaving like I'm using some sort of copy of the variable $foo inside the while loop and I am modifying only that particular copy. Here's a complete test program: #!/bin/bash set -e set -u foo=0 bar="hello" if [[ "$bar" == "hello" ]] then foo=1 echo "Setting \$foo to 1: $foo" fi echo "Variable \$foo after if statement: $foo" lines="first line\nsecond line\nthird line" echo -e $lines | while read line do if [[ "$line" == "second line" ]] then foo=2 echo "Variable \$foo updated to $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 to 1: 1 # Variable $foo after if statement: 1 # Value of $foo in while loop body: 1 # Variable $foo updated to 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)

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