head
Overview¶
kgtk head is analogous to the POSIX 'head' command. It takes optional input
and output files, and a primary option, -n N.
When -n N is positive, it will pass just the first N data edges of a KGTK
input file to the KGTK output file.
When -n N is negative, it will pass all except the last N edges of the KGTK
input file to the KGTK output file.
The header record, cotaining the column names, is always passed and is not included in the edge limit, N.
Multiplier suffixes are not supported.
This command defaults to --mode=NONE since it doesn't attach special meaning
to particular columns.
Although a positive -n N has the same effect as KgtkReader's record_limit
option, this code currently implements the limit itself.
Usage¶
usage: kgtk head [-h] [-i INPUT_FILE] [-o OUTPUT_FILE] [-n EDGE_LIMIT]
[-v [optional True|False]]
This utility is analogous to the POSIX "head" command.
When "-n N" is positive, it will pass just the first N data edges of a KGTK input file to the KGTK output file.
When "-n N" is negative, it will pass all except the last N edges of the KGTK input file to the KGTK output file.
The header record, cotaining the column names, is always passed and is not included in N.
Multiplier suffixes are not supported.
Use this command to filter the output of any KGTK command:
kgtk xxx / head -n 20
Use it to limit the records in a file:
kgtk head -i file.tsv -o file.html
This command defaults to --mode=NONE so it will work with TSV files that do not follow KGTK column naming conventions.
Additional options are shown in expert help.
kgtk --expert head --help
optional arguments:
-h, --help show this help message and exit
-i INPUT_FILE, --input-file INPUT_FILE
The KGTK input file. (May be omitted or '-' for
stdin.)
-o OUTPUT_FILE, --output-file OUTPUT_FILE
The KGTK output file. (May be omitted or '-' for
stdout.)
-n EDGE_LIMIT, --edges EDGE_LIMIT
The number of records to pass if positive
(default=10).
-v [optional True|False], --verbose [optional True|False]
Print additional progress messages (default=False).
Examples¶
See the First 10 Edges¶
Using the default value for -n N:
kgtk head -i examples/docs/head-example1.tsv
| node1 | label | node2 | id |
|---|---|---|---|
| red | property | True | |
| red | isa | rgbcolor | |
| red | maxoccurs | 1 | |
| green | property | True | |
| green | isa | rgbcolor | |
| green | maxoccurs | 1 | |
| blue | property | True | |
| blue | isa | rgbcolor | |
| blue | maxoccurs | 1 | |
| rgbcolor | datatype | True |
See the First 15 Edges¶
kgtk head -n 15 -i examples/docs/head-example1.tsv
| node1 | label | node2 | id |
|---|---|---|---|
| red | property | True | |
| red | isa | rgbcolor | |
| red | maxoccurs | 1 | |
| green | property | True | |
| green | isa | rgbcolor | |
| green | maxoccurs | 1 | |
| blue | property | True | |
| blue | isa | rgbcolor | |
| blue | maxoccurs | 1 | |
| rgbcolor | datatype | True | |
| rgbcolor | node1_type | symbol | |
| rgbcolor | node2_type | number | |
| rgbcolor | minval | 0.0 | |
| rgbcolor | maxval | 1.0 | |
| rgbcolor | requires | red |
See All Except the Last 20 Edges¶
kgtk head -n -20 -i examples/docs/head-example1.tsv
| node1 | label | node2 | id |
|---|---|---|---|
| red | property | True | |
| red | isa | rgbcolor | |
| red | maxoccurs | 1 | |
| green | property | True | |
| green | isa | rgbcolor | |
| green | maxoccurs | 1 | |
| blue | property | True | |
| blue | isa | rgbcolor | |
| blue | maxoccurs | 1 | |
| rgbcolor | datatype | True | |
| rgbcolor | node1_type | symbol | |
| rgbcolor | node2_type | number | |
| rgbcolor | minval | 0.0 | |
| rgbcolor | maxval | 1.0 | |
| rgbcolor | requires | red | |
| rgbcolor | requires | green | |
| rgbcolor | requires | blue | |
| rgbcolor | isa | colorclass | |
| rgbcolor | prohibits | colorname | |
| colorname | property | True | |
| colorname | isa | colorclass | |
| colorname | node1_type | symbol | |
| colorname | node2_type | symbol | |
| colorname | node2_values | red | |
| colorname | node2_values | green | |
| colorname | node2_values | blue | |
| colorname | node2_values | yellow |
See the Complete File¶
Using a very large number, we can use kgtk head to display
the entire file.
kgtk head -n 999999999 -i examples/docs/head-example1.tsv
| node1 | label | node2 | id |
|---|---|---|---|
| red | property | True | |
| red | isa | rgbcolor | |
| red | maxoccurs | 1 | |
| green | property | True | |
| green | isa | rgbcolor | |
| green | maxoccurs | 1 | |
| blue | property | True | |
| blue | isa | rgbcolor | |
| blue | maxoccurs | 1 | |
| rgbcolor | datatype | True | |
| rgbcolor | node1_type | symbol | |
| rgbcolor | node2_type | number | |
| rgbcolor | minval | 0.0 | |
| rgbcolor | maxval | 1.0 | |
| rgbcolor | requires | red | |
| rgbcolor | requires | green | |
| rgbcolor | requires | blue | |
| rgbcolor | isa | colorclass | |
| rgbcolor | prohibits | colorname | |
| colorname | property | True | |
| colorname | isa | colorclass | |
| colorname | node1_type | symbol | |
| colorname | node2_type | symbol | |
| colorname | node2_values | red | |
| colorname | node2_values | green | |
| colorname | node2_values | blue | |
| colorname | node2_values | yellow | |
| colorclass | mustoccur | True | |
| cube | property | True | |
| cube | isa | boxshape | |
| cone | property | True | |
| cone | isa | pointyshape | |
| cone | isa | roundshape | |
| sphere | property | True | |
| sphere | isa | roundshape | |
| pyramid | property | True | |
| pyramid | isa | pointyshape | |
| cylinder | property | True | |
| cylinder | isa | roundshape | |
| boxshape | datatype | True | |
| boxshape | isa | shape | |
| pointyshape | datatype | True | |
| pointyshape | isa | shape | |
| roundshape | datatype | True | |
| roundshape | isa | shape | |
| shape | datatype | True | |
| shape | mustoccur | True |