docs: def find(file):
      '''tries to find ``file`` using OS-specific searches and some guessing'''
      # Try MacOS Spotlight:
      mdfind = which('mdfind')
      if mdfind:
          out = run([mdfind,'-name',file],stderr=None,quiet=None)
          if out.return_code==0 and out.output:
                  for fname in out.output.split('\n'):
                      if os.path.basename(fname)==file:
                          return fname
  
      # Try UNIX locate:
      locate = which('locate')
      if locate:
          out = run([locate,file],stderr=None,quiet=None)
          if out.return_code==0 and out.output:
              for fname in out.output.split('\n'):
                  if os.path.basename(fname)==file:
                      return fname
  
      # Try to look through the PATH, and some guesses:
      path_search = os.environ["PATH"].split(os.pathsep)
      path_search += ['/usr/local/afni','/usr/local/afni/atlases','/usr/local/share','/usr/local/share/afni','/usr/local/share/afni/atlases']
      afni_path = which('afni')
      if afni_path:
          path_search.append(os.path.dirname(afni_path))
      if nl.wrappers.fsl.bet2:
          path_search.append(os.path.dirname(nl.wrappers.fsl.bet2))
      for path in path_search:
          path = path.strip('"')
          try:
              if file in os.listdir(path):
                  return os.path.join(path,file)
          except:
              pass