Parameters:
A parameter is a name, a digit, or any of the characters *, @, #, ?, -, $, and !\^. So, what's the difference between a name and a parameter exactly? Not much actually, it's all in the usage. If a word follows a command, as in: ls -l word , then word is one of the parameters (or arguments) passed to the ls command. But if the ls command was inside a sh script, then in all likelihood the word would also be a variable name. So a parameter can be a name when passing information into some other command or script. Viewed from inside a script however, the command line arguments appear as a line of positional parameters named by digits in the ordered sequence of arrival (See - Script Example_1.1 ). So a parameter can also be a digit. The other characters listed are special characters which are assigned values at script start up and may be used if required from within a script.
Well after reading through the above, I am still not sure if this is any clearer. Lets see if an example can help to clarify things a little.
Script example_1.1 - The shell default parameters
<b>#!/bin/sh -vx
#######################################################
# example_1.1 (c) R.H.Reepe 1996 March 28 Version 1.0 #
#######################################################
echo "Script name is [$0]"
echo "First Parameter is [$1]"
echo "Second Parameter is [$2]"
echo "This Process ID is [$]"
echo "This Parameter Count is [$#]"
echo "All Parameters [$@]"
echo "The FLAGS are [$-]"</b>
If you execute the script shown above with some arguments as shown below, you will get the output on your screen that follows.
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