Bash background processes, function and local variables example

	#!/bin/bash
	#This simple code demonstrates how to define a function, local and global variables in bash.
	#And most importantly, how to launch background processes and wait for their termination
	gvar="Glob value"
	ncalls=0
	avar="Test"
	# Note for ksh users: in ksh to mark a function definition you should use either function keyword
	# or () after the function name, not both
	function a_proc(){
	echo ${gvar}
	local avar=$1 #ksh users: use 'typeset' instead of 'local'
	echo "Input: ${avar}"
	sleep 100
	avar=$(date)
	echo "Output: ${avar}"
	ncalls=$((${ncalls} + 1))
	}
	a_proc "$(date)" &
	a_proc "$(date)" &
	a_proc "$(date)" &
	a_proc "$(date)" &
	a_proc "$(date)" &
	a_proc "$(date)" &
	wait
	#Although I am trying to update ${ncalls} assuming that this will change my global variable, but ...
	#This is because I am launching the function in background, which works in a subshell,
	#so global variables won't be updated
	echo "ncalls=${ncalls}"
	echo "avar=${avar}"
	##But look what happens with ncalls when launched in foreground
	a_proc "$(date)"
	echo "ncalls=${ncalls}"
	##Conclusion: the local keyword (for bash, use typeset for ksh) can be useful if you want to make sure that you are not
	##changing a global variable in your function

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