BASH tr command

Question

Id like to convert it to uppercase for the simple purpose of formatting so it will adhere to a future case statement. As I thought case statements are case sensitive.

I see all over the place the tr command used in concert with echo commands to give you immediate results such as:

echo "Enter in Location (i.e. SDD-134)"
read answer # user enters "cfg"

echo $answer | tr '[:lower:]' '[:upper:]' # which produced

cfg # first echo not upper?

echo $answer #echo it again and it is now upper...

CFG

R

I fail to see how this code could ever change $answer - you don't assign the output of tr back to $answer, so $answer should STAY cfg. – Baines

first echo is upper for me. second is not – Vanesavanessa

Did you have a question? – Anchoress

I see what I did wrong and also I now understand the above and below answers given. I mistakenly had a test line of code later in the script. THANKS for the assistance =) – R

What is with the Down Vote? I only turned to SO when I found multiple websites and forums with the wrong direction and use of tr that I did not want. – R

You're being downvoted because the first sentence in your question is not at all clear. What is it that you're hoping to do, and what is the problem? – Squinty

Answer 1

This version doesn't require bash, but uses a pipe:

read -p "Enter in Location (i.e. SDD-134) " answer
answer=$(echo "$answer" | tr '[:lower:]' '[:upper:]')
echo "$answer"

And if you're using bash and don't care about portability you can replace the second line with this:

answer="${answer^^}"

Check the "Parameter Expansion" section of bash's man page for details.

Tropaeolin

Answer 2

Echoing a variable through tr will output the value, it won't change the value of the variable:

answer='cfg'
echo $answer | tr '[:lower:]' '[:upper:]'
# outputs uppercase but $answer is still lowercase

You need to reassign the variable if you want to refer to it later:

answer='cfg'
answer=$(echo $answer | tr '[:lower:]' '[:upper:]')
echo $answer
# $answer is now uppercase

Pogge

so the echo after: answer$(echo <---- does not echo in the shell? – R

Correct, it does not get output. It gets captured and assigned back to the variable. – Pogge

Answer 3

In bash version 4 or greater:

answer=${answer^^*}

Vernal

Answer 4

It is not clear what you are asking, but if you are trying to convert the user input to uppercase, just do:

sed 1q | tr '[:lower:]' '[:upper:]' | read answer

In shells that do not run the read in a subshell (eg zsh), this will work directly. To do this in bash, you need to do something like:

printf "Enter in Location (i.e. SDD-134): "
sed 1q | tr '[:lower:]' '[:upper:]' | { read answer; echo $answer; }

After the subshell closes, answer is an unset variable.

Fieldstone

In bash you could just say read answer < <(tr '[:lower:]' '[:upper:]'<<<"$answer") and avoid the pipe that way. – Endive

Answer 5

good and clear way to uppercase variable is

$var=`echo $var|tr '[:lower:]' '[:upper:]'`

Note Bene a back quotes

Makeup

This is not valid syntax for assignment; you should omit the first $ – Endive