#!/bin/sh -u
# Show the equivalence of nested IF statements and ELIF
# Syntax:
#  $0 pathname
# Purpose:
#  Process the pathname and tell some things about it.
#  Do different things for files and directories.
# -IAN! idallen@idallen.ca

# Use standard search path, friendly umask, ASCII collating and sorting.
# Set the language and character set to be ASCII/C standard.
#
PATH=/bin:/usr/bin ; export PATH
LC_COLLATE=C ; export LC_COLLATE
LANG=C ; export LANG
umask 022

# Make sure this script is called with exactly one argument.
#
if [ $# -ne 1 ] ; then
    echo 1>&2 "$0: Expecting one pathname argument; found $# ($*)"
    exit 1
fi

# Code using nested IF statements requires two levels of indentation:
#
if [ -f "$1" ] ; then
    echo "Argument '$1' is a file name."
    if [ -s "$1" ]; then
        not='not '
    else
        not=''
    fi
    echo "The file is ${not}empty."
else
    if [ -d "$1" ] ; then
        echo "Argument '$1' is a directory name."
        if [ -w "$1" ]; then
            not=''
        else
            not='not '
        fi
        echo "The directory is ${not}writable by you."
    else
        echo "Argument '$1' is not an accessible directory or file name."
    fi
fi

# Code using ELIF statements requires less indentation:
#
if [ -f "$1" ] ; then
    echo "Argument '$1' is a file name."
    if [ -s "$1" ]; then
        not='not '
    else
        not=''
    fi
    echo "The file is ${not}empty."
elif [ -d "$1" ] ; then
    echo "Argument '$1' is a directory name."
    if [ -w "$1" ]; then
        not=''
    else
        not='not '
    fi
    echo "The directory is ${not}writable by you."
else
    echo "Argument '$1' is not an accessible directory or file name."
fi

# this script exits with the return code of the last command executed