alias l="l.sh" => use simply l instead of ls or less

l.sh

#!/bin/bash

LSCMD="ls --color=auto -lahF"
LESSCMD="less"

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

# with argument :

if [ ! -e "$1" ]; then
    echo "$1 does not exist."
elif [ -f "$1" ]; then
    # $1 is a file
    $LESSCMD "$1"
elif [ -d "$1" ]; then
    # $1 is a directory
    $LSCMD "$1"
fi