A variable modified inside a while loop is not remembered

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

The while loop is executed in a subshell. So any changes you do to the variable will not be available once the subshell exits.

Instead you can use a here string to re-write the while loop to be in the main shell process; only echo -e $lines will run in a subshell:

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 -e "$lines")"

You can get rid of the rather ugly echo in the here-string above by expanding the backslash sequences immediately when assigning lines. The $'...' form of quoting can be used there:

lines=$'first line\nsecond line\nthird line'
while read line; do
    ...
done <<< "$lines"

More Related Contents:

  1. Are shell scripts sensitive to encoding and line endings?
  2. Difference between sh and Bash
  3. Pass commands as input to another command (su, ssh, sh, etc)
  4. Why would a correct shell script give a wrapped/truncated/corrupted error message? [duplicate]
  5. Why is testing “$?” to see if a command succeeded or not, an anti-pattern?
  6. Reading quoted/escaped arguments correctly from a string
  7. Why does my Bash code fail when I run it with ‘sh’?
  8. What is the benefit of using $() instead of backticks in shell scripts? [duplicate]
  9. How to pipe input to a Bash while loop and preserve variables after loop ends
  10. How can I remove the extension of a filename in a shell script?
  11. I just assigned a variable, but echo $variable shows something else
  12. How can I declare and use Boolean variables in a shell script?
  13. How do I run a shell script without using “sh” or “bash” commands?
  14. Bash variable scope
  15. Ubuntu says “bash: ./program Permission denied” [closed]
  16. Using variables inside a bash heredoc
  17. Assignment of variables with space after the (=) sign?
  18. How to get a password from a shell script without echoing
  19. How does Ctrl-C terminate a child process?
  20. Deleting lines from one file which are in another file
  21. How to do a logical OR operation for integer comparison in shell scripting?
  22. What does it mean in shell when we put a command inside dollar sign and parentheses: $(command)
  23. Reading key/value parameters from a file into a shell script
  24. When should I double-quote a parameter expansion? [duplicate]
  25. Forward function declarations in a Bash or a Shell script?
  26. Is there an elegant way to store and evaluate return values in bash scripts?
  27. Syntax for a single-line while loop in Bash
  28. Looping through find output in Bash where file name contains white spaces
  29. How to break out of a loop in Bash?
  30. ^word^replacement^ on all matches in Bash?

Leave a Comment