For information on available commands, see impala-shell Command Reference. You can see the full set of available commands by pressing TAB twice:

[impalad-host:21000] >
connect   describe  explain   help      history   insert    quit      refresh   select    set       shell     show      use       version
[impalad-host:21000] >

  Note: Commands must be terminated by a semi-colon. A command can span multiple lines.

For example:

[impalad-host:21000] > select * from alltypessmall limit 5
Query: select * from alltypessmall limit 5
Query finished, fetching results ...
2009    3       50      true    0       0       0       0       0       0       03/01/09        0       2009-03-01 00:00:00
2009    3       51      false   1       1       1       10      1.100000023841858       10.1    03/01/09        1       2009-03-01 00:01:00
2009    3       52      true    2       2       2       20      2.200000047683716       20.2    03/01/09        2       2009-03-01 00:02:00.100000000
2009    3       53      false   3       3       3       30      3.299999952316284       30.3    03/01/09        3       2009-03-01 00:03:00.300000000
2009    3       54      true    4       4       4       40      4.400000095367432       40.4    03/01/09        4       2009-03-01 00:04:00.600000000
Returned 5 row(s) in 0.10s
[impalad-host:21000] >