tail

Overview¶

kgtk tail is analogous to the POSIX 'tail' command. It takes optional input and output files, and a primary option, -n N.

For -n N, it will pass just the last N data edges of a KGTK input file to the KGTK output file.

The POSIX 'tail' command's notion of '-n +N' is not supported.

The POSIX 'tail' command's notion of waiting for changes to the input file is not supported.

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.

Usage¶

usage: kgtk tail [-h] [-i INPUT_FILE] [-o OUTPUT_FILE] [-n EDGE_LIMIT]
                 [-v [optional True|False]]

This utility is analogous to the POSIX "head" command. 

For "-n N", pass just the last N data edges of a KGTK input file to the KGTK output file. 

"-n +N" does not have the special meaning it has in the POSIC "tail" command. 

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 / tail -n 20 

Use it to limit the records in a file: 

kgtk tail -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 html --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 (default=10).

  -v [optional True|False], --verbose [optional True|False]
                        Print additional progress messages (default=False).

Examples¶

See the Last 10 Edges¶

Using the default value for -n N:

kgtk tail -i examples/docs/tail-example1.tsv

node1	label	node2
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

See the Last 15 Edges¶

kgtk tail -n 15 -i examples/docs/tail-example1.tsv

node1	label	node2
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

See the Complete File¶

Using a very large number, we can use kgtk tail to display the entire file. However, this will buffer the entire file in memory, which may not be feasible for large files.

kgtk tail -n 999999999 -i examples/docs/tail-example1.tsv

node1	label	node2
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