I have the following situation:
#!/bin/bash
echo "Please enter a word:"
read foobar
The script is getting called with sh script.sh in the Ubuntu terminal.
Searching on the internet for solutions I found:
foobar=${foobar,,}
echo $foobar
The above approach does only work with bash script.sh
So I went on researching and found:
echo $foobar | tr '[:upper:]' '[:lower:]'
Which does indeed work for both, bash and sh, but without the echo it does not work.
It also prints the read input two times instead of one like so:
Y
y
So how can I do this for sh without printing the read input twice?
It's probably because you didn't assign the translated output to a variable yet. Also I suggest quoting your variables around doublequotes to prevent word splitting and pathname expansion.
foobar=$(echo "$foobar" | tr '[:upper:]' '[:lower:]')
If you're using case and you just need to check if an input is y or Y either way you can use a glob pattern like this. There's no need to transliterate it to lowercase form.
case $foobar in
[yY])
echo "User said yes."
;;
*)
echo "User said no."
;;
esac
Also you can somehow suppress showing user input by using -s:
read -s foobar
As a whole to make your code work well in both bash and sh you should already remove the part which is bash specific:
#!/bin/bash
echo "Please enter a word:"
read -s foobar
foobar=$(echo "$foobar" | tr '[:upper:]' '[:lower:]')
echo "$foobar"
And if it's just about showing the smaller form, you can skip the assignment. But don't use another echo along with it:
#!/bin/bash
echo "Please enter a word:"
read -s foobar
echo "$foobar" | tr '[:upper:]' '[:lower:]'
Another alternative form from case. This is meant to be POSIX compatible.
if [ "$foobar" = y ] || [ "$foobar" = Y ]; then
echo "User said yes."
else
echo "User said no."
fi
In bash it could be simply like this. It would work even in earlier versions that doesn't support ${parameter,,} feature.
if [[ $foobar == [yY] ]]; then
echo "User said yes."
else
echo "User said no."
fi