#!/bin/sh -u
# A "backup" script - Non-Structured Programming Version (many exits).
# Specifications:
#  - processes exactly one plain file name (not a directory)
#  - file name must be readable
#  - copy file to file.bak, if file.bak does not already exist
#
# NOTE: This script fragment is incomplete - it does not follow all
# the script guidelines set out in "script_style.txt".
#
# -IAN! idallen@idallen.ca

# Check argument count.
#
if [ $# -eq 0 ] ; then
        echo 1>&2 "$0: expecting exactly one file name - none found"
        exit 4
fi
if [ $# -ne 1 ] ; then
        echo 1>&2 "$0: expecting exactly one file name, found $# ($*)"
        exit 4
fi

# Test for readable
#
if [ ! -r "$1" ] ; then
        echo 1>&2 "$0: path '$1' is missing or is not readable"
        exit 3
fi
echo "path $1 is readable"

# Test for plain file
#
if [ ! -f "$1" ] ; then
        echo 1>&2 "$0: path '$1' is not a plain file"
        exit 2
fi
echo "path $1 is is a plain file"

# Test for existence of .bak file; abort if already there
#
if [ -e "$1.bak" ] ; then
        echo 1>&2 "$0: path '$1.bak' already exists"
        echo 1>&2 "$0: nothing copied"
        exit 1
fi

# Finally!  Do the copy.  Test the exit code for failure.
#
if cp -p "$1" "$1.bak" ; then
    echo "File '$1' copied to '$1.bak'.  Good job."
else
    status=$?
    echo 1>&2 "$0: failed to copy '$1' to '$1.bak': status $status"
    exit $status
fi