merge_intervals.sh

# sample input: 10-1000,15-350,50-1500,2100,1700-1800,45,40,145,2-1300
set -o pipefail
tr , '\n' | sort -n | awk '
BEGIN {
        FS = OFS = "-"
}
NF < 1 || NF > 2 || (NF == 2 && $1 > $2) {
        print "bad input: " $0 | "cat >&2"
        exit 1
}
NF == 1 {
        $2 = $1
}
$2 <= end {
        next
}
$1 <= end {
        end = $2
        next
}
{
        emit()
        start = $1
        end = $2
}
END {
        emit()
}
function emit() {
  if (NR != 1) {
    if (start == end)
      print start
    else
      print start, end
  }
}' | paste -sd,