The filter specifiers each specify a processing step which is performed on a table, transforming an input table to an output one. You can have any combination of them, and they are used in the order that they are given on the command line. They are like filter-type commands in a Unix pipeline. Some of them have additional optional or mandatory arguments.
-select <expr>
<expr>
evaluates to true.
The syntax is like in TOPCAT,
as described in
SUN/253.
Columns can be addressed by name (if the name is syntactically a java
identifier) case-independently, or as $n
,
where n is the column
index. $1
is the first column.
$0
is the row index (starting at 1).
-sort [-down] [-nullsfirst] <colid-list>
<colid-list>
. <colid-list>
is a space-separated list of column identifiers
(names, $identifiers or numbers, where 1 is the first column).
One or more columns may be specified: sorting is done on the
values in the first-specified field, but if they are equal the
tie is resolved by looking at the second-specified field, and so on.
If the -down
flag is used,
the sort order is descending instead
of ascending. If the -nullsfirst
flag is used, blank
entries are considered to come at the start of the collation sequence
instead of the end.
-sortexpr <expr>
-every <step>
<step>
'th row,
starting with the first row.
-head <nrows>
<nrows>
rows of the table.
-tail <nrows>
<nrows>
rows of the table.
-addcol [-after <col-id> | -before <col-id>]
<col-name> <expr>
<col-name>
defined by the algebraic expression
<expr>
.
Expression syntax is as for the -select
flag. By default
the new row appears after the last row of the table, but you
can position it using either the -after
or
-before
flags. In either
case, identify a column using its name (if it is syntactically
a java identifier), or its number (the first column is 1), or
its $identifier ($1
is the first column).
-keepcols <colid-list>
<colid-list>
, in that order.
<colid-list>
is space-separated. Column identifier
syntax is as for -addcol
flag.
-delcols <colid-list>
<colid-list>
is as for -keepcols
flag.
-explode
-cache
-random
-sequential