如何从Bash变量中修剪空格？

variable="  Hello World!  "
trimmed_variable="${variable#"${variable%%[![:space:]]*}"}"
trimmed_variable="${trimmed_variable%"${trimmed_variable##*[![:space:]]}"}"
echo "$trimmed_variable"

variable="  Hello World!  "
trimmed_variable=$(echo "$variable" | sed -e 's/^[[:space:]]*//' -e 's/[[:space:]]*$//')
echo "$trimmed_variable"

variable="  Hello World!  "
trimmed_variable=$(echo "$variable" | awk '{$1=$1;print}')
echo "$trimmed_variable"

variable="  Hello World!  "
trimmed_variable=$(echo "$variable" | tr -d '[:space:]')
echo "$trimmed_variable"

variable="  Hello World!  "
trimmed_variable=$(echo "$variable" | xargs)
echo "$trimmed_variable"