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## B.41 `tpipe`: Performs pipeline processing on a table

`tpipe` performs all kinds of general purpose manipulations which take one table as input. It is extremely flexible, and can do the following things amongst others:

- calculate statistics
- display metadata
- select rows in various ways, including algebraically
- define new columns as algebraic functions of old ones
- delete or rearrange columns
- sort rows
- convert between table formats

and combine these operations. You can think of it as a supercharged table copying tool.

The basic operation of `tpipe` is that it reads an input table, performs zero or more processing steps on it, and then does something with the output. There are therefore three classes of things you need to tell it when it runs:

Input table location
  Specified by the `in`, `ifmt` and `istream` parameters.
Processing steps
  Either provide a string giving steps as the value of one or more `cmd` parameters, or the name of a file containing the steps using the `script` parameter. The steps that you can perform are described in Section 6.1.
Output table destination
  What happens to the output table is determined by the value of the `omode` parameter. By default, `omode=out`, in which case the table is written to a new table file in a format determined by `ofmt`. However, you can do other things with the result such as calculate the per-column statistics (`omode=stats`), view only the table and column metadata (`omode=meta`), display it directly in TOPCAT (`omode=topcat`) etc.

See Section 6 for a more detailed explanation of these ideas.

The parameters mentioned above are listed in detail in the next section.

- B.41.1 Usage
- B.41.2 Examples

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STILTS - Starlink Tables Infrastructure Library Tool Set
Starlink User Note256
STILTS web page: http://www.starlink.ac.uk/stilts/
Author email: m.b.taylor@bristol.ac.uk
Mailing list: topcat-user@jiscmail.ac.uk