问如何使用expect脚本返回scp命令的输出？

EN

   wait [args]
         delays until a spawned process (or the current process if none is
         named) terminates.

         wait normally returns a list of four integers.  The first integer
         is the pid of the process that was waited upon.  The second inte-
         ger is the corresponding spawn id.  The third integer is -1 if an
         operating system error occurred, or 0 otherwise.   If  the  third
         integer  was  0, the fourth integer is the status returned by the
         spawned process.  If the third integer was -1, the fourth integer
         is  the  value  of errno set by the operating system.  The global
         variable errorCode is also set.

         Additional elements may appear at the end  of  the  return  value
         from  wait.   An  optional  fifth  element  identifies a class of
         information.  Currently, the only possible value for this element
         is  CHILDKILLED in which case the next two values are the C-style
         signal name and a short textual description.

         The -i flag declares the process to  wait  corresponding  to  the
         named  spawn_id  (NOT the process id).  Inside a SIGCHLD handler,
         it is possible to wait for any spawned process by using the spawn
         id -1.

         The  -nowait  flag causes the wait to return immediately with the
         indication of a successful wait.  When the process exits (later),
         it  will automatically disappear without the need for an explicit
         wait.

         The wait command may also be used wait for a forked process using
         the  arguments  "-i  -1".  Unlike its use with spawned processes,
         this command can be executed at any time.  There  is  no  control
         over  which  process is reaped.  However, the return value can be
         checked for the process id.