Passing arguments to commands

Most applications accept arguments in different formats. Suppose -p and -v are the options available, and -k N is another option that takes a number. Also, the command requires a filename as argument. This application can be executed in multiple ways:

• $ command -p -v -k 1 file
• $ command -pv -k 1 file
• $ command -vpk 1 file
• $ command file -pvk 1
  

Within a script, the command-line arguments can be accessed by their position in the command line. The first argument will be $1, the second $2, and so on.
This script will display the first three command line arguments:

echo $1 $2 $3

It's more common to iterate through the command arguments one at a time. The shift command shifts eachh argument one space to the left, to let a script access each argument as $1. The following code displays all the command-line values:

$ cat showArgs.sh
for i in `seq 1 $#`
do
echo $i is $1
shift
done
$ sh showArgs.sh a b c
1 is a
2 is b
3 is c