#!/bin/ksh -p

awk 'BEGIN {
	tabs = 0;
}

function printline(i)
{
	for (ii = 1; ii <= i; ii++) {
		printf "\t"
	}
	printf "%s\n",$0
}

/^[ 	]*#if/ {
	printline(tabs);
	tabs ++;
	next;
}
/^[ 	]*(#else|#elif)/ {
	printline(tabs - 1);
	next;
}

/^[ 	]*#endif/ {
	tabs --;
	if (tabs < 0)
		print "error: unmatched #endif";
	printline(tabs);
	next;
}

{
	printline(tabs);
}' $1