dbrep.1.3

#!/bin/sh
# File: dbrep.1.3
# System: D.B.SHDB.1
# Dependencies: -
# ------------------------------------------------
# Author: Daniel Bullimore
# Authors Email: - 
# First Written: 2013
# ------------------------------------------------
# !If you make changes add your name to the list
# Last Modified (d/m/y): 
# 4/5/2019 Daniel Bullimore
# 9/5/2019 daniel bullimore 
# 11/5/2019 daniel bullimore
# ------------------------------------------------
# Copyright 2019 Daniel Bullimore
# D.B.SHDB is licensed under the The 3-Clause BSD License
# To view this license:
# https://github.com/DanielBullimore/D.B.SHDB/blob/master/LICENSE
#
#--------------
#---DISCRIPTION\
#---------------
# Replaces the value of given key in database file
# Checks null parameters, database exists and can be read/written
# Insures no other replace functions are in action
# exits on 1 on parameter/state errors
# reads database file line by line searching for replace key
# writes all non matching pairs to temp file
# once found the matching key is written to temp with new value
# when all lines copied a check is made for the replacement having taken place
# over writes database file with new temp file if replacement took place
# returns error if replace key was not matched.
#------------------
# Notes
#------------------
# Unique/random temp file name would allow more than one replace case to be run at the same time.

if [ -z "$1" ] || [ -z "$2" ] || [ -z "$3" ]
 then
	echo "Syntax: db rep <row_key> <new_value> <db_file>";
	exit 1;
 elif [ ! -f "$3" ]
 then
	echo "Error: database not found";
	exit 1;
 elif [ ! -r "$3" ] || [ ! -w "$3" ]
 then
	echo "Error: can not read or write from database file: $3";
	exit 1;
 else
	if [ ! -f "$3.temp" ]
	 then
		touch "$3.temp";
	 else
		echo "Error: File IO colision";	
		exit 1;
	fi;
	FOUND="FALSE";
	while read f
	 do
		KEY=$(echo "$f" | cut -d\	 -f1);
		if [ "$KEY" = "$1" ]
		 then
	#found=>
			echo "$1	$2" >> "$3.temp"; 
			FOUND="TRUE";
		 else
			 echo "$f" >> "$3.temp";
		fi;
	done < "$3";
	if [ "$FOUND" = "TRUE" ]
	 then 
		mv "$3.temp" "$3";
	 else
		echo "Error: Key not found";
		exit 1;
	fi;	
fi;