How to convert a string from uppercase to lowercase in Bash?
This question already has an answer here:
If you are using bash 4 you can use the following approach:
x="HELLO"
echo $x # HELLO
y=${x,,}
echo $y # hello
z=${y^^}
echo $z # HELLO
Use only one , or ^ to make the first letter lowercase or uppercase .
The correct way to implement your code is
y="HELLO"
val=$(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"
Why not execute in backticks ?
x=`echo "$y" | tr '[:upper:]' '[:lower:]'`
This assigns the result of the command in backticks to the variable x . (ie it's not particular to tr but is a common pattern/solution for shell scripting)
You can use $(..) instead of the backticks. See here for more info.
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