Positional Parameters

When a program is executed with a list of options and arguments,
  these are passed in as positional parameters.

Command examines and determines validity of option/argument.

They can be referenced with the $ followed by the index in the list.

$0 - indicates the program itself. 

Additional parameters are numbered sequentially.

$0-$9 can be directly referenced.

Use {} to reference values > 9. bash
   echo ${11}

Maximum parameter limit, 
  count = 0x7FFFFFFF or 2Gig. (2^31)
  length = page-size * 32 (page = 4k?) ~ 128K
  /usr/include/linux/binfmts.h

shift - shifts arguments left (down by 1). Discards previous $1.
  Old way of handling 10 or more arguments. 

Quoted strings treated as single argument if referenced right.
  Use quotes around argument inside script i.e "$1"

Accessing whole argument list except $0

$* - lists all arguments. Quotes on arguments stripped 
  - list treated as individual words.

"$*" - lists all arguments. Quotes on arguments stripped 
  - then whole list treated as single long string.

$@ - lists all arguments. Quotes on arguments stripped 
  - list treated as individual words.

"$@" - lists all arguments. Quotes on arguments not stripped 
  - quotes honored.


#!/bin/bash

#save this in a file such as arglister.sh
#  and make it executable, then as follows :  
#  ./arglister.sh one "and two" and a three

echo using '$*'
for arg in $*
do 
  echo $arg
done

echo ""
echo using '"$*"'
for arg in "$*"
do 
  echo $arg
done

echo ""
echo using '$@'
for arg in $@
do 
  echo $arg
done

echo ""
echo using '"$@"'
for arg in "$@"
do 
  echo $arg
done



Positional parameters are useful when writing shell scripts and functions.