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### B.27.1 Usage

The usage of `tcatn` is

       stilts <stilts-flags> tcatn nin=<count> ifmtN=<in-format> inN=<tableN>
                                   icmdN=<cmds> ocmd=<cmds>
                                   omode=out|meta|stats|count|cgi|discard|topcat|samp|plastic|tosql|gui
                                   out=<out-table> ofmt=<out-format>
                                   seqcol=<colname> loccol=<colname>
                                   uloccol=<colname> countrows=true|false

If you don't have the `stilts` script installed, write "`java -jar stilts.jar`" instead of "`stilts`" - see Section 3. The available `<stilts-flags>` are listed in Section 2.1. For programmatic invocation, the Task class for this command is `uk.ac.starlink.ttools.task.TableCatN`.

Parameter values are assigned on the command line as explained in Section 2.3. They are as follows:

`countrows = true|false` (Boolean)
  Whether to count the rows in the table before starting the output. This is essentially a tuning parameter - if writing to an output format which requires the number of rows up front (such as normal FITS) it may result in skipping the number of passes through the input files required for processing. Unless you have a good understanding of the internals of the software, your best bet for working out whether to set this true or false is to try it both ways

  [Default: `false`]

`icmdN = <cmds>` (ProcessingStep[])
  Specifies processing to be performed on input table #N as specified by parameter `inN`, before any other processing has taken place. The value of this parameter is one or more of the filter commands described in Section 6.1. If more than one is given, they must be separated by semicolon characters (";"). This parameter can be repeated multiple times on the same command line to build up a list of processing steps. The sequence of commands given in this way defines the processing pipeline which is performed on the table.

  Commands may alteratively be supplied in an external file, by using the indirection character '@'. Thus a value of "`@filename`" causes the file `filename` to be read for a list of filter commands to execute. The commands in the file may be separated by newline characters and/or semicolons, and lines which are blank or which start with a '`#`' character are ignored.

`ifmtN = <in-format>` (String)
  Specifies the format of input table #N as specified by parameter `inN`. The known formats are listed in Section 5.1.1. This flag can be used if you know what format your table is in. If it has the special value `(auto)` (the default), then an attempt will be made to detect the format of the table automatically. This cannot always be done correctly however, in which case the program will exit with an error explaining which formats were attempted. This parameter is ignored for scheme-specified tables.

  [Default: `(auto)`]

`inN = <tableN>` (StarTable)
  The location of input table #N. This may take one of the following forms:
  - A filename.
  - A URL.
  - The special value "`-`", meaning standard input. In this case the input format must be given explicitly using the `ifmtN` parameter. Note that not all formats can be streamed in this way.
  - A scheme specification of the form `:<scheme-name>:<scheme-args>`.
  - A system command line with either a "`<`" character at the start, or a "`|`" character at the end ("`<syscmd`" or "`syscmd|`"). This executes the given pipeline and reads from its standard output. This will probably only work on unix-like systems.
  In any case, compressed data in one of the supported compression formats (gzip, Unix compress or bzip2) will be decompressed transparently.
`loccol = <colname>` (String)
  Name of a column to be added to the output table which will contain the location (as specified in the input parameter(s)) of the input table from which each row originated.
`nin = <count>` (Integer)
  The number of input tables for this task. For each of the input tables N there will be associated parameters `ifmtN`, `inN` and `icmdN`.
`ocmd = <cmds>` (ProcessingStep[])
  Specifies processing to be performed on the output table, after all other processing has taken place. The value of this parameter is one or more of the filter commands described in Section 6.1. If more than one is given, they must be separated by semicolon characters (";"). This parameter can be repeated multiple times on the same command line to build up a list of processing steps. The sequence of commands given in this way defines the processing pipeline which is performed on the table.

  Commands may alteratively be supplied in an external file, by using the indirection character '@'. Thus a value of "`@filename`" causes the file `filename` to be read for a list of filter commands to execute. The commands in the file may be separated by newline characters and/or semicolons, and lines which are blank or which start with a '`#`' character are ignored.

`ofmt = <out-format>` (String)
  Specifies the format in which the output table will be written (one of the ones in Section 5.1.2 - matching is case-insensitive and you can use just the first few letters). If it has the special value "`(auto)`" (the default), then the output filename will be examined to try to guess what sort of file is required usually by looking at the extension. If it's not obvious from the filename what output format is intended, an error will result.

  This parameter must only be given if `omode` has its default value of "`out`".

  [Default: `(auto)`]

`omode = out|meta|stats|count|cgi|discard|topcat|samp|plastic|tosql|gui` (ProcessingMode)
  The mode in which the result table will be output. The default mode is `out`, which means that the result will be written as a new table to disk or elsewhere, as determined by the `out` and `ofmt` parameters. However, there are other possibilities, which correspond to uses to which a table can be put other than outputting it, such as displaying metadata, calculating statistics, or populating a table in an SQL database. For some values of this parameter, additional parameters (`<mode-args>`) are required to determine the exact behaviour.

  Possible values are

  - `out`
  - `meta`
  - `stats`
  - `count`
  - `cgi`
  - `discard`
  - `topcat`
  - `samp`
  - `plastic`
  - `tosql`
  - `gui`
  Use the `help=omode` flag or see Section 6.4 for more information.

  [Default: `out`]

`out = <out-table>` (TableConsumer)
  The location of the output table. This is usually a filename to write to. If it is equal to the special value "-" (the default) the output table will be written to standard output.

  This parameter must only be given if `omode` has its default value of "`out`".

  [Default: `-`]

`seqcol = <colname>` (String)
  Name of a column to be added to the output table which will contain the sequence number of the input table from which each row originated. This column will contain 1 for the rows from the first concatenated table, 2 for the second, and so on.
`uloccol = <colname>` (String)
  Name of a column to be added to the output table which will contain the unique part of the location (as specified in the input parameter(s)) of the input table from which each row originated. If not null, parameters will also be added to the output table giving the pre- and post-fix string common to all the locations. For example, if the input tables are "/data/cat_a1.fits" and "/data/cat_b2.fits" then the output table will contain a new column <colname> which takes the value "a1" for rows from the first table and "b2" for rows from the second, and new parameters "<colname>_prefix" and "<colname>_postfix" with the values "/data/cat_" and ".fits" respectively.

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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