-- try this

[b]-- this will export all the rows[/b]

C:>exp mag/mag tables=(emp)

Export: Release 8.1.6.0.0 - Production on Tue Mar 11 09:21:32 2003

(c) Copyright 1999 Oracle Corporation.  All rights reserved.

Connected to: Oracle8i Enterprise Edition Release 8.1.6.0.0 - Production
With the Partitioning option
JServer Release 8.1.6.0.0 - Production
Export done in WE8ISO8859P1 character set and WE8ISO8859P1 NCHAR character set

About to export specified tables via Conventional Path ...
. . exporting table                            EMP         12 rows exported
Export terminated successfully without warnings.

[b]-- export 4 rows[/b]

C:>exp mag/mag tables=(emp) query="where rownum < 5 "

Export: Release 8.1.6.0.0 - Production on Tue Mar 11 09:21:43 2003

(c) Copyright 1999 Oracle Corporation.  All rights reserved.

Connected to: Oracle8i Enterprise Edition Release 8.1.6.0.0 - Production
With the Partitioning option
JServer Release 8.1.6.0.0 - Production
Export done in WE8ISO8859P1 character set and WE8ISO8859P1 NCHAR character set

About to export specified tables via Conventional Path ...
. . exporting table                            EMP          4 rows exported
Export terminated successfully without warnings.

[b]-- export 8 rows[/b]

C:>exp mag/mag tables=(emp) query="where rownum < 9 "

Export: Release 8.1.6.0.0 - Production on Tue Mar 11 09:21:49 2003

(c) Copyright 1999 Oracle Corporation.  All rights reserved.

Connected to: Oracle8i Enterprise Edition Release 8.1.6.0.0 - Production
With the Partitioning option
JServer Release 8.1.6.0.0 - Production
Export done in WE8ISO8859P1 character set and WE8ISO8859P1 NCHAR character set

About to export specified tables via Conventional Path ...
. . exporting table                            EMP          8 rows exported
Export terminated successfully without warnings.

C:>