Dmax - Selection of the maximum/minimum value records
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Dmax [ -g group-by-key ] [ options ] key-field-list [ input-file.. ]
Dmax
selects record[s] of which
key-field-list value
is maximum within the whole input files.
If there are more than one record having
maximum key value, all the records are
selected keeping input record sequence.
Note that Dmax may select all the records in the
input files, when the records have same key value.
In this case, you need memory to hold all the input records.
Especially, this may happen when you give wrong field name.
You can select minimum key value records
by giving r key flag or
by giving -v option.
Key value evaluation follows the value comparison
rule of D-commands.
See
Comparison of values
section of Dintro.
- -F
- adds "filename" field to each output record;
maximum key value records are selected from each input file.
- -g group-by-key-field-list
-
group by process;
maximum key value records are selected each time
when the group by key value is changed.
Usually, you need to sort input file before group by process.
- -k key-flags
- default key-flags for both
key-field-list and group-by-key-field-list.
Note that this default value has effect only for the fields which
have no key-flags in the list.
See the manual of
Dintro.
- -v
- select the minimum value records instead of maximum value.
Multiple occurence of -v toggles the effect.
- -D [i/o]datautf=8|16|32
- UTF I/O feature (see manual page of
UTF I/O feature.)
Select count field (numeric) max record.
Dmax count:n
Select minimum record (count field: numeric).
Dmax -v count:n
For each id value, select the last date,time value records.
Dmax -g id date,time
- filename:
- at the top of each record,
when
-F
option is specified.
Value is the input file name
in the form of the command arguments after globbed by the shell.
This field is not added when the input file is the standard input.
- Ddatautf, Didatautf, Dodatautf
- for
UTF I/O feature.
See the manual of
D_msg.
Dintro,
Dmeans,
D_msg.
AUTHOR
MIYAZAWA Akira
miyazawa@nii.ac.jp
2006