#!/bin/bash

# Function (put them first)
isroot() {
	myUser=$(whoami)
	if [ $myUser = root ]
	then
		echo "You are root"
	else
		echo "You are user myUser"
	fi
}

#
# Start here
#

# Arguments are $1 $2 $3 etc

echo Program name: $0, Number of args: $#

# By default arg will be all command line parameters

for arg
do
	echo $arg
done

# Variables

mine=Hello
mineOther=" World !"
concated=$mine$mineOther
echo Var set to $concated

# Numbers

let "first=1"
let "first=first+1"
echo First incremented to $first

# for loop. Double brackets mean maths not strings

for ((i=0; i<4; i++)) 
do

	# The [ ] invokes program 'test'
	if [ $first -eq $i ]  # integer comparison
	then	
		echo Found first: $first to equal i: $i
	elif [ $i -lt 1 ]
	then
		echo Working directory is $(pwd)
	else
		true	# Do nothing
	fi

done

# Method call

isroot

# Take text as comand line input until THE_MARKER

cat > crib-test.txt << THE_MARKER
This,is,a,test
on,several,lines
into,a,file
THE_MARKER

# Simple file processing

for line in $(cat crib-test.txt)
do
	echo The line is: $line
	second=$(echo $line | awk -F , '{print $2}')  # The -F tells awk what field separator to use, default to space
	echo Second field: $second
done

# Process processing

procDetails=$(ps -Ao pid,pcpu,cmd | grep -v PID | sort -n -k 2 | tail -1 | awk '{print "Process "$1" is using highest percentage of "$2" pct with command "$3}')
memDetails=$(ps -Ao pid,pmem,cmd | grep -v PID | sort -n -k 3 | tail -1 | awk '{print "Process "$1" is using highest memory of "$2" pct with command "$3}')
echo Processor details: $procDetails
echo Memory details: $memDetails