Unix Lab 6

Unix Lab Exercise 6

Introduction to Unix - POS420

Parameter Variables

These are some of the variables you have to know. All these variables having a prefix $ are called parameter variables.

These are some of the variables we have to know.

$# number of arguments on the command line

$0 the name of the current shell or program 

$1 the first argument

$2 the second argument

..

..

$9 the ninth argument

$* all arguments on the command line ("$1 $2 ... $9")

$@ all arguments on the command line, each separately quoted ($1 $2 ..)

$ cat script3.sh

if [ $# -lt 3 ]

then

echo "Please enter at least three names"

exit

fi

echo "You entered $# names"

echo "The first name is $1"

echo "The second name is $2"

echo "The third name is $3"

echo "this script name is $0"

echo "You have entered these names: $*"

echo "You have entered these names: $@"

Let us run

$ chmod +x script3.sh

$ ./script3.sh tom

Please enter at least three names

$ script3.sh tom smith kay scott

You entered 4 names

The first name is tom

The second name is smith

The third name is kay

This script name is script3.sh

You have entered these names: tom smith kay scott

You have entered these names: tom smith kay scott

Let us run one more time with quotes for a name since there is a space in one name

$ script3.sh kay ron 'tom smith'

You entered 3 names

The first name is kay

The second name is ron

The third name is tom smith

this script name is script3.sh

You have entered these names: kay ron tom smith

You have entered these names: kay ron tom smith

Another example :Enter the following shell script in vi editor.

$ cat variables.sh

echo "$#:" $#

echo '$#:' $#

echo '$-:' $-

echo '$?:' $?

echo '$$:' $$

echo '$!:' $!

echo '$3:' $3

echo '$0:' $0

echo '$*:' $*

echo '$@:' $@

When executed with some arguments it displays the values for the shell variables, e.g.:

$ ./variables.sh one two three...