.. index:: --libxo, xo
The "xo" Utility
================
The `xo` utility allows command line access to the functionality of
the libxo library. Using `xo`, shell scripts can emit XML, JSON, and
HTML using the same commands that emit text output.
The style of output can be selected using a specific option: "-X" for
XML, "-J" for JSON, "-H" for HTML, or "-T" for TEXT, which is the
default. The "--style <style>" option can also be used. The standard
set of "--libxo" options are available (see :ref:`options`), as well
as the `LIBXO_OPTIONS`_ environment variable.
.. _`LIBXO_OPTIONS`: :ref:`libxo-options`
The `xo` utility accepts a format string suitable for `xo_emit` and
a set of zero or more arguments used to supply data for that string::
xo "The {k:name} weighs {:weight/%d} pounds.\n" fish 6
TEXT:
The fish weighs 6 pounds.
XML:
<name>fish</name>
<weight>6</weight>
JSON:
"name": "fish",
"weight": 6
HTML:
<div class="line">
<div class="text">The </div>
<div class="data" data-tag="name">fish</div>
<div class="text"> weighs </div>
<div class="data" data-tag="weight">6</div>
<div class="text"> pounds.</div>
</div>
The `--wrap $path` option can be used to wrap emitted content in a
specific hierarchy. The path is a set of hierarchical names separated
by the '/' character::
xo --wrap top/a/b/c '{:tag}' value
XML:
<top>
<a>
<b>
<c>
<tag>value</tag>
</c>
</b>
</a>
</top>
JSON:
"top": {
"a": {
"b": {
"c": {
"tag": "value"
}
}
}
}
The `--open $path` and `--close $path` can be used to emit
hierarchical information without the matching close and open
tag. This allows a shell script to emit open tags, data, and
then close tags. The `--depth` option may be used to set the
depth for indentation. The `--leading-xpath` may be used to
prepend data to the XPath values used for HTML output style::
EXAMPLE;
#!/bin/sh
xo --open top/data
xo --depth 2 '{:tag}' value
xo --close top/data
XML:
<top>
<data>
<tag>value</tag>
</data>
</top>
JSON:
"top": {
"data": {
"tag": "value"
}
}
When making partial lines of output (where the format string does not
include a newline), use the `--continuation` option to let secondary
invocations know they are adding data to an existing line.
When emitting a series of objects, use the `--not-first` option to
ensure that any details from the previous object (e.g. commas in JSON)
are handled correctly.
Use the `--top-wrap` option to ensure any top-level object details are
handled correctly, e.g. wrap the entire output in a top-level set of
braces for JSON output.
EXAMPLE;
#!/bin/sh
xo --top-wrap --open top/data
xo --depth 2 'First {:tag} ' value1
xo --depth 2 --continuation 'and then {:tag}\n' value2
xo --top-wrap --close top/data
TEXT:
First value1 and then value2
HTML:
<div class="line">
<div class="text">First </div>
<div class="data" data-tag="tag">value1</div>
<div class="text"> </div>
<div class="text">and then </div>
<div class="data" data-tag="tag">value2</div>
</div>
XML:
<top>
<data>
<tag>value1</tag>
<tag>value2</tag>
</data>
</top>
JSON:
{
"top": {
"data": {
"tag": "value1",
"tag": "value2"
}
}
}
Lists and Instances
-------------------
A "*list*" is set of one or more instances that appear under the same
parent. The instances contain details about a specific object. One
can think of instances as objects or records. A call is needed to
open and close the list, while a distinct call is needed to open and
close each instance of the list.
Use the `--open-list` and `--open-instances` to open lists and
instances. Use the `--close-list` and `--close-instances` to close
them. Each of these options take a `name` parameter, providing the
name of the list and instance.
In the following example, a list named "machine" is created with three
instances:
opts="--json"
xo $opts --open-list machine
NF=
for name in red green blue; do
xo $opts --depth 1 $NF --open-instance machine
xo $opts --depth 2 "Machine {k:name} has {:memory}\n" $name 55
xo $opts --depth 1 --close-instance machine
NF=--not-first
done
xo $opts $NF --close-list machine
The normal `libxo` functions use a state machine to help these
transitions, but since each `xo` command is invoked independent of the
previous calls, the state must be passed in explicitly via these
command line options.
Command Line Options
--------------------
::
Usage: xo [options] format [fields]
--close <path> Close tags for the given path
--close-instance <name> Close an open instance name
--close-list <name> Close an open list name
--continuation OR -C Output belongs on same line as previous output
--depth <num> Set the depth for pretty printing
--help Display this help text
--html OR -H Generate HTML output
--json OR -J Generate JSON output
--leading-xpath <path> Add a prefix to generated XPaths (HTML)
--not-first Indicate this object is not the first (JSON)
--open <path> Open tags for the given path
--open-instance <name> Open an instance given by name
--open-list <name> Open a list given by name
--option <opts> -or -O <opts> Give formatting options
--pretty OR -p Make 'pretty' output (add indent, newlines)
--style <style> Generate given style (xml, json, text, html)
--text OR -T Generate text output (the default style)
--top-wrap Generate a top-level object wrapper (JSON)
--version Display version information
--warn OR -W Display warnings in text on stderr
--warn-xml Display warnings in xml on stdout
--wrap <path> Wrap output in a set of containers
--xml OR -X Generate XML output
--xpath Add XPath data to HTML output);
Example
-------
::
% xo 'The {:product} is {:status}\n' stereo "in route"
The stereo is in route
% ./xo/xo -p -X 'The {:product} is {:status}\n' stereo "in route"
<product>stereo</product>
<status>in route</status>