node-tab: Unix-style tables for command-line utilities

This module implements functions for reading and writing Unix-style command line
tables. The model mimics that of traditional Unix commands like "ps", which
emit a table with a default set of columns that can be customized using command
line options. This module implements facilities to both ingest and emit these
tables.

Output overview

$3

To write a simple table to stdout:

var mod_tab = require('tab');

mod_tab.emitTable({
'columns': [ 'PID', 'TTY', 'TIME', 'CMD' ],
'rows': [
[ '60881', 'ttys000', '0:00.19', '-bash' ],
[ '61674', 'ttys000', '0:00.17', 'vim README.md' ]
]
});

This outputs:

PID TTY TIME CMD
60881 ttys000 0:00.19 -bash
61674 ttys000 0:00.17 vim README.md

$3

You can send this to a stream like stderr instead by specifying the 'stream'
property:

mod_tab.emitTable({
'stream': process.stderr,
'columns': [ 'PID', 'TTY', 'TIME', 'CMD' ],
'rows': [
[ '60881', 'ttys000', '0:00.19', '-bash' ],
[ '61674', 'ttys000', '0:00.17', 'vim README.md' ]
]
});

$3

To make the output look more like ps(1), you could specify field widths and
alignments:

mod_tab.emitTable({
'columns': [ {
'label': 'PID',
'align': 'right',
'width': 6
}, {
'label': 'TTY',
'width': 7
}, {
'label': 'TIME',
'align': 'right',
'width': 10
}, {
'label': 'CMD'
} ],

'rows': [
[ '60881', 'ttys000', '0:00.19', '-bash' ],
[ '61674', 'ttys000', '0:00.17', 'vim README.md' ]
]
});

This would output:

``
PID TTY TIME CMD
60881 ttys000 0:00.19 -bash
61674 ttys000 0:00.17 vim README.md
``

$3

If you want, data (rows) can be specified with objects instead of arrays, where
the object keys keys correspond to field labels. This example outputs the same
as the previous one:

mod_tab.emitTable({
'columns': [ {
'label': 'PID',
'align': 'right',
'width': 6
}, {
'label': 'TTY',
'width': 7,
}, {
'label': 'TIME',
'align': 'right',
'width': 10
}, {
'label': 'CMD'
} ],

'rows': [ {
'PID': '60881',
'TTY': 'ttys000',
'TIME': '0:00.19',
'CMD': '-bash'
}, {
'PID': '61674',
'TTY': 'ttys000',
'TIME': '0:00.17',
'CMD': 'vim README.md'
} ]
});

$3

Instead of accumulating the data in memory and emitting the whole table, you can
create a TableOutputStream object with the field configuration and then emit
individual records:

var out = new mod_tab.TableOutputStream({
'columns': [ 'PID', 'TTY', 'TIME', 'CMD' ]
});

out.writeRow([ '60881', 'ttys000', '0:00.19', '-bash' ]);

/ or /

out.writeRow({
'PID': '61674',
'TTY': 'ttys000',
'TIME': '0:00.17',
'CMD': 'vim README.md'
});

$3

You can also omit the header row or change the column and row separators:

mod_tab.emitTable({
'columns': [ 'name', 'passwd', 'uid', 'gid', 'gecos', 'home', 'shell' ],
'columnSeparator': ':',
'rowSeparator': ';\n',
'omitHeader': true,
'rows': [
[ 'root', '*', '0', '0', 'Admin', '/var/root', '/bin/sh' ],
[ 'nobody', '*', '-2', '-2', 'Unpriv', '/var/empty', '/usr/bin/false' ]
]
});

Input overview

The goal of the input interface is to ingest such tables as either objects or
arrays (as desired).

To ingest streaming tabular input, create a TableInputStream and listen for the
"row" event:

var input = new mod_tab.TableInputStream({
'stream': process.stdin,
'columns': [ 'pid', 'tty', 'time', 'cmd' ]
});

input.on('row', console.log);

For the above outputs, this would emit:

{ pid: '60881',
tty: 'ttys000',
time: '0:00.19',
cmd: '-bash' }
{ pid: '61674',
tty: 'ttys000',
time: '0:00.17',
cmd: 'vim README.md' }

If the first row is the header row, you can leave off "columns":

var input = new mod_tab.TableInputStream({ 'stream': process.stdin });
input.on('row', console.log);

Pipe "ps" to that and get:

{ PID: '60881',
TTY: 'ttys000',
TIME: '0:00.19',
CMD: '-bash' }
{ PID: '61674',
TTY: 'ttys000',
TIME: '0:00.17',
CMD: 'vim README.md' }

You could get arrays instead by specifying the 'format' property:

var input = new mod_tab.TableInputStream({
'format': 'array',
'stream': process.stdin,
});

input.on('row', function (row) {
console.log(row);
});

This would emit:

[ '60881', 'ttys000', '0:00.19', '-bash' ]
[ '61674', 'ttys000', '0:00.17', 'vim README.md' ]

You can also specify a different delimiter from the default (which is any
whitespace) using a string or regular expression for the 'delim' property, as
in:

/ split on colons instead of whitespace /
var input = new mod_tab.TableInputStream({
'delim': ':'
'stream': process.stdin,
'columns': [ 'pid', 'tty', 'time', 'cmd' ]
});

/ split on semicolon or comma /
var input = new mod_tab.TableInputStream({
'delim': /[,;]/,
'stream': process.stdin,
'columns': [ 'pid', 'tty', 'time', 'cmd' ]
});