Remove duplicate entries in UNIX path. Keeps the order of first occurences.

uniqpath.awk

#!/usr/bin/awk -f

BEGIN {
  RS = ":|\n"
}

{
  if (data[$0]++ == 0)
    lines[++count] = $0
}

END {
  for (i=1; i<=count; i++) {
    printf "%s", lines[i]
    if (i < count)
      printf ":"
  }
}