 "dscl . -search /Users UniqueID <id>" returns 
  //    <name> UniqueID = (
  //      <id>
  //    )
  // "dscl . -search /Groups PrimaryGroupID <id>" returns
  //    <name> PrimaryGroupID = (
  //      <id>
  //    )
  // The following method returns a command that uses sed to process the
  // the result and returns "<name> <id>" to simulate one entry returned
  // by MAC_GET_ALL_USERS_CMD or MAC_GET_ALL_GROUPS_CMD.
  // For certain negative id case like nfsnobody, the <id> is quoted as
  // "<id>", added one sed section to remove the quote.
  // Specifically, the method returns:
  // dscl . -search /Users UniqueID <id> | sed 'N;s/\\n//g;N;s/\\n//g' | sed 's/UniqueID =//g' | sed 's/)//g' | sed 's/\"//g'
  // OR
  // dscl . -search /Groups PrimaryGroupID <id> | sed 'N;s/\\n//g;N;s/\\n//g' | sed 's/PrimaryGroupID =//g' | sed 's/)//g' | sed 's/\"//g'
 "dscl . -search /Users UniqueID <id>" returns 
  //    <name> UniqueID = (
  //      <id>
  //    )
  // "dscl . -search /Groups PrimaryGroupID <id>" returns
  //    <name> PrimaryGroupID = (
  //      <id>
  //    )
  // The following method returns a command that uses sed to process the
  // the result and returns "<name> <id>" to simulate one entry returned
  // by MAC_GET_ALL_USERS_CMD or MAC_GET_ALL_GROUPS_CMD.
  // For certain negative id case like nfsnobody, the <id> is quoted as
  // "<id>", added one sed section to remove the quote.
  // Specifically, the method returns:
  // dscl . -search /Users UniqueID <id> | sed 'N;s/\\n//g;N;s/\\n//g' | sed 's/UniqueID =//g' | sed 's/)//g' | sed 's/\"//g'
  // OR
  // dscl . -search /Groups PrimaryGroupID <id> | sed 'N;s/\\n//g;N;s/\\n//g' | sed 's/PrimaryGroupID =//g' | sed 's/)//g' | sed 's/\"//g' | ShellBasedIdMapping.java