SHELL SCRIPTING - ARGUMENTS / POSITIONAL PARAMETERS

In this series of Shell Scripting, today we discuss about command line arguments also know as positional parameters.
To handle options on the command line, we use a facility in the shell called positional parameters. Positional parameters are a series of special variables ($0 through $9) that contain the contents of the command line.
For Example:
[swapnil@googlinux.com]$ myprog.sh Swapnil Jain Indore
If myprog.sh
is a shell script, we could read each item on the command line because the positional parameters contain the following:
$0
would contain"myprog.sh"
$1
would contain"Swapnil"
$2
would contain"Jain"
$3
would contain"Indore"
Here is a simple script you would like to try:
#!/bin/bash
echo "Program Name is $0"
echo "First Name is $1"
echo "Last Name is $2"
echo "City is $3"
Output:
[swapnil@googlinux.com]$ ./myprog.sh Swapnil Jain Indore
Program Name is ./myprog.sh
First Name is Swapnil
Last Name is Jain
City is Indore
IMPROVING YOUR SCRIPT
You can further improve this script by using some help and error handling
#!/bin/bash
if [ $# -lt 3 ];then
echo "ERROR: minimum 3 paramerts required"
echo "Example: myprog.sh fname lname city"
else
echo "Program Name is $0"
echo "First Name is $1"
echo "Last Name is $2"
echo "City is $3"
fi
$#
- contains the total number of parameters
You can play a lot with shell script, create simple programs to automate task. Stay tuned for more. Thats it for positional parameters.
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