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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

library “libxo”

SYNOPSIS

#include <libxo/xo.h>

int
xo_open_container(const char *name);

int
xo_open_container_h(xo_handle_t *handle, const char *name);

int
xo_open_container_hd(xo_handle_t *handle, const char *name);

int
xo_open_container_d(const char *name);

int
xo_close_container(const char *name);

int
xo_close_container_h(xo_handle_t *handle, const char *name);

int
xo_close_container_hd(xo_handle_t *handle);

int
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");
        xo_emit("{:host-name/%s%s%s", hostname,
                domainname ? "." : "", domainname ?: "");
        xo_close_container("system");
        xo_close_container("top");

    Sample Output:
      Text:
        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}0, 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);

    xo_open_container("top");
    ...
    xo_close_container_d();

SEE ALSO

xo_emit(3), libxo(3)

HISTORY

The libxo library first appeared in FreeBSD 11.0.

AUTHORS

libxo was written by Phil Shafer <phil@freebsd.org>.