for

• A for is used to loop through a set of values. The loop sets a variable to each value in the list and then the loop is executed once for each value.
• The basic format for a for-loop in shell is:

  for var in value1 value2 value3
  do
      command
      command
  done
  

• In shell, you may put as many statements inside the for as you would like.
• The do and the done are required, even if there is only one statement to execute.
• Inside the loop, the variable is set to each word.
• Here's an example:

  for i in 1 2 3 "the end"
  do
      echo "i is " $i
  done
  

  The output from running this for loop will be:

  i is 1
  i is 2
  i is 3
  i is the end
  

• Notice the values don't have to be numbers - it is just a list of values.
• If you want whitespace in one of the values, put it in double quotes, like "the end".

• There are newer versions of for-loops in many shells - which are supported in yours?
• How can you write a standard counting loop in your shell? In other words, how can you do math?
  

• This loop will set a variable called arg to each of the arguments passed into the shell script and then print each one on a line by itself:
  

• The "${@}" has special meaning to the shell. It means "all of the arguments". Don't worry too much about it right now - just use it when your code needs to access all of the arguments.