#!/bin/sh -u
#
#     $0 pathname
#
# A script that identifies if the pathname given on the command line
# is a file, is non-empty, is readable, and is writable.
# Nonexistent and non-files are silently ignored.
#
# WARNING: Many of the comments in this file are "Instructor-Type"
#   comments and are *not* appropriate for real scripts.  Do not put
#   "Instructor-Type" comments into the scripts that you submit for marking.
#   I put them in my example files because I am teaching you how to
#   write scripts; do not submit my teaching comments back to me again.
#   Read the week7.txt notes for more details on good comment style.
#
# -IAN! idallen@ncf.ca  June 2001

# All scripts must start with lines similar to these two:
#
export PATH=/bin:/usr/bin
umask 022

# Validate the script arguments.
# Output what the extra arguments were, to help the user.
#
if [ "$#" -ne 1 ]; then
	echo 1>&2 "$0: Expecting exactly one argument; found $# ($*)"
	exit 1
fi

# Test four conditions in four nested 'if' statements.
# (You can also combine these into a single statement; but, it doesn't
# read any better and isn't significantly faster.)
# Pathnames failing any of the tests are silently ignored.
#
# With this much indentation, the "echo" message runs off the right edge
# of the screen in the source file here unless we put it in a variable
# and use that in the "echo" command:
#
message="File '$1' is not empty, is readable, and is writable"

if [ -f "$1" ]; then
	if [ -s "$1" ]; then
		if [ -r "$1" ]; then
			if [ -w "$1" ]; then
				echo "$message"
			fi
		fi
	fi
fi

# Test the same four conditions using four non-nested 'if' statements.
# This has the same effect; but, much less indentation is needed.
# We exit the script if any of the four conditions is *NOT* true.
# If we make it to the end of the script, all the conditions must be true.
#
if [ ! -f "$1" ]; then
	exit 1		# is not a file
fi
if [ ! -s "$1" ]; then
	exit 1		# has no size (is empty)
fi
if [ ! -r "$1" ]; then
	exit 1		# is not readable
fi
if [ ! -w "$1" ]; then
	exit 1		# is not writable
fi

echo "$message"		# it passed all the tests!

exit 0