How to convert a string from uppercase to lowercase in Bash? [duplicate]
The correct way to implement your code is
y="HELLO"val=$(echo "$y" | tr '[:upper:]' '[:lower:]')string="$val world"This uses $(...) notation to capture the output of the command in a variable. Note also the quotation marks around the string variable -- you need them there to indicate that $val and world are a single thing to be assigned to string.
If you have bash 4.0 or higher, a more efficient & elegant way to do it is to use bash builtin string manipulation:
y="HELLO"string="${y,,} world"
Note that tr can only handle plain ASCII, making any tr-based solution fail when facing international characters.
Same goes for the bash 4 based ${x,,} solution.
The awk tool, on the other hand, properly supports even UTF-8 / multibyte input.
y="HELLO"val=$(echo "$y" | awk '{print tolower($0)}')string="$val world"Answer courtesy of liborw.