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LIBXO(3) FreeBSD Library Functions Manual LIBXO(3)
NAME
xo_open_container, xo_open_container_h, xo_open_container_hd,
xo_open_container_d xo_close_container, xo_close_container_h,
xo_close_container_hd, xo_close_container_d - open (and close) container
constructs
LIBRARY
Text, XML, JSON, and HTML Output Emission Library (libxo, -lxo)
SYNOPSIS
#include <libxo/xo.h>
xo_ssize_t
xo_open_container(const char *name);
xo_ssize_t
xo_open_container_h(xo_handle_t *handle, const char *name);
xo_ssize_t
xo_open_container_hd(xo_handle_t *handle, const char *name);
xo_ssize_t
xo_open_container_d(const char *name);
xo_ssize_t
xo_close_container(const char *name);
xo_ssize_t
xo_close_container_h(xo_handle_t *handle, const char *name);
xo_ssize_t
xo_close_container_hd(xo_handle_t *handle);
xo_ssize_t
xo_close_container_d(void);
DESCRIPTION
libxo represents two types of hierarchy: "containers" and "lists". A
container appears once under a given parent where a list contains
instances that can appear multiple times. A container is used to hold
related fields and to give the data organization and scope. The
container has no value, but serves to contain other nodes.
To open a container, call xo_open_container() or xo_open_container_h().
The former uses the default handle and the latter accepts a specific
handle.
To close a level, use the xo_close_container() or xo_close_container_h()
functions.
Each open call should have a matching close call. If the XOF_WARN flag
is set and the name given does not match the name of the currently open
container, a warning will be generated.
Example:
xo_open_container("top");
xo_open_container("system");
my-host.example.org
XML:
<top>
<system>
<host-name>my-host.example.org</host-name>
</system>
</top>
JSON:
"top" : {
"system" : {
"host-name": "my-host.example.org"
}
}
HTML:
<div class="data"
data-tag="host-name">my-host.example.org</div>
EMITTING HIERARCHY
To create a container, use the xo_open_container() and
xo_close_container() set of functions. The handle parameter contains a
handle such as returned by xo_create(3) or NULL to use the default
handle. The name parameter gives the name of the container, encoded in
UTF-8. Since ASCII is a proper subset of UTF-8, traditional C strings
can be used directly.
The close functions with the "_d" suffix are used in "Do The Right Thing"
mode, where the name of the open containers, lists, and instances are
maintained internally by libxo to allow the caller to avoid keeping track
of the open container name.
Use the XOF_WARN flag to generate a warning if the name given on the
close does not match the current open container.
For TEXT and HTML output, containers are not rendered into output text,
though for HTML they are used when the XOF_XPATH flag is set.
EXAMPLE:
xo_open_container("system");
xo_emit("The host name is {:host-name}\n", hn);
xo_close_container("system");
XML:
<system><host-name>foo</host-name></system>
DTRT MODE
Some users may find tracking the names of open containers, lists, and
instances inconvenient. libxo offers a "Do The Right Thing" mode, where
libxo will track the names of open containers, lists, and instances so
the close function can be called without a name. To enable DTRT mode,
turn on the XOF_DTRT flag prior to making any other libxo output.
xo_set_flags(NULL, XOF_DTRT);
Each open and close function has a version with the suffix "_d", which
will close the open container, list, or instance:
xo_open_container("top");
...
xo_close_container_d();
Note that the XOF_WARN flag will also cause libxo to track open
containers, lists, and instances. A warning is generated when the name
given to the close function and the name recorded do not match.
libxo was written by Phil Shafer <phil@freebsd.org>.
FreeBSD 14.0-RELEASE-p11 December 4, 2014 FreeBSD 14.0-RELEASE-p11