getopts tutorial in Shell Script

This shell script shows how to use getopts in shell script to get command line options in your own shell scripts. In this example, the following options are programmed.

-c clear the screen
-d show list of files in current working directory
-m start mc (midnight commander shell) , if installed
-e { editor } start this { editor } if installed

    #
# Function to clear the screen
#
cls()
{
    clear
    echo "Clear screen, press a key . . ."
    read
    return
}

#
# Function to show files in current directory 
#
show_ls()
{   
    ls
    echo "list files, press a key . . ."
    read
    return
}

#
# Function to start mc
#
start_mc()
{
    if which mc > /dev/null ; then
	mc
	echo "Midnight commander, Press a key . . ."
	read
    else
	echo "Error: Midnight commander not installed, Press a key . . ."
	read
    fi		
    return
}

#
# Function to start editor 
#
start_ed()
{
    ced=$1
    if which $ced > /dev/null ; then
	$ced
	echo "$ced, Press a key . . ."
	read
    else
	echo "Error: $ced is not installed or no such editor exist, Press a key . . ."
	read
    fi		
    return
}

#
# Function to print help
#
print_help_uu()
{
	   echo "Usage: $0 -c -d -m -v {editor name}"; 
	   echo "Where -c clear the screen";
	   echo "      -d show dir";
	   echo "      -m start midnight commander shell";
	   echo "      -e {editor}, start {editor} of your choice";
	   return
}

#
# Main procedure start here
#
# Check for sufficent args
#

if [ $# -eq 0 ] ; then
    print_help_uu
    exit 1
fi    

#
# Now parse command line arguments
#
while getopts cdme: opt
do
    case "$opt" in
	c) cls;;
	d) show_ls;;
	m) start_mc;;
	e) thised="$OPTARG"; start_ed $thised ;;
	\?) print_help_uu; exit 1;; 
    esac
done