The for Loop

General form:
for variable-name in value1 value2
do
commands
done

• The control words for, do and done MUST come at the beginning of a command line (more exactly: they must follow a command separator; space in between is allowed)
• The for loop as well as the other control structures can be run directly from the shell, too. Upon recognizing an incomplete for the shell responds with the secondary prompt until it encounters done.
• The combination
  for i in $*,
  which lets the variable i in turn take each of the command line arguments, occurs so frequently that the shell accepts the abbreviation
  for i
  for it. More precisely, this is the same as
  for i in "$@"
• Generating values for a for loop
  • List the values explicitly after in, as in
    for animal in cat dog bird
  • Take the values from shell script arguments, as in
    for i in $*or equivalent for i
  • Take filenames from a directory as values. The shell expands combinations involving * and ? into filenames.
    for file in CC/*.cc
    do
    mv $file old$file
    done
    Note the difference between
    for name in $*
    and
    for name in *
  • Take values from a shell variable.
    HOSTS="host1 host2 host3"
    for HOST in $HOSTS
    
  • Take values from the output of a command.
    for name in `cat animals`
    do
    echo $name is an animal
    done