foo(input) {
  echo "$input"
}
foo("hello world");

foo() {
  echo "$1"
}
foo "hello world"

Shell script functions behave just like scripts and other commands:

• They always take a 0 to N parameters, referred to with $1, $2 etc. They can not declare parameters by name.
• They are executed using name arg1 arg2, and not with parentheses as C-like languages.

None.