Grep sources for system includes (e.g. for AC_CHECK_HEADERS in configure.ac)

headers.sh

#!/usr/bin/env bash

# Grep sources for system includes; e.g. for AC_CHECK_HEADERS:
# $ echo "AC_CHECK_HEADERS([$(./headers.sh | tr '\n' ' ')])" >> configure.ac
#
# @param ... - source files/directories
grep_for_includes()
{
	grep -h '#include[ ]*<' $@ | sort | uniq | while read
	do
		REPLY=${REPLY#*<}
		echo ${REPLY%>}
	done
}

grep_for_includes ${@:-*.c *.h}