TAKE stage v1.0

Pipelines v1.9

Purpose, Operands, Streams used, Usage notes, Examples, See also

Home

Syntax

 _FIRST_ _1_______
>>__TAKE__ _|_______|__|_________|_ ___________________________________________________><
 | |_LAST__| |_numrecs_| |
 |_ _ALL_ ________________|
 |_*___|

Purpose

Use the TAKE stage to select one or more records from the beginning or end of its primary input stream. TAKE copies the selected records to its primary output stream. If its secondary output stream is connected, TAKE copies all other records to its secondary output stream, otherwise it discards the unselected records.

Operands

●	FIRST select records from the beginning of the input stream. This is the default.
●	LAST select records from the end of the input stream.
●	ALL * specifies that all input records are selected and written to the primary output stream.
●	numrecs is an unsigned integer which specifies the number of records to be selected from the input stream. The default is 1. If you specify 0 for numrecs, TAKE copies all of its input records to its secondary output stream, if it is connected, otherwise TAKE discards the records and the stage ends.

Streams used

The following streams are used by the TAKE stage:

Stream	Action
Primary input stream	TAKE reads records from its primary input stream.
Primary output stream	TAKE copies the selected records to its primary output stream.
Secondary output stream	TAKE copies the unselected records to its secondary output stream, if it is connected.

Usage notes

1)	TAKE FIRST does not delay the records. TAKE LAST delays the specified number of records.
2)	TAKE LAST stores the specified number of records in a buffer. For each subsequent input record (if any), TAKE LAST writes the record residing longest in the buffer to the secondary output stream, if it is connected. Otherwise, it discards the record. The input record is then stored in the buffer, queued on a first-in, first-out basis. When end-of-file is reached on the primary input stream, TAKE LAST writes the specified number of records from the buffer to the primary output stream, if it is connected, otherwise it discards the records.
3)	If the TAKE stage discovers that all of its output streams are not connected, the TAKE stage ends.
4)	TAKE FIRST disconnects its primary output stream before it writes the unselected records to its secondary output stream. TAKE LAST disconnects its secondary output stream before writing the records to its primary output stream.
5)	TAKE verifies that its secondary input stream is not connected and then begins execution.

Examples

The following pipeline reads the file in.txt and displays on the console only record number 10.

pipe < in.txt
 | drop first 9
 | take 1
 | console

See also

Reference the following links for additional information:

DROP, FROMLABEL, HOLE, TOLABEL