LIBXO(3)               FreeBSD Library Functions Manual               LIBXO(3)

NAME
     xo_open_list, xo_open_list_h, xo_open_list_hd, xo_open_list_d
     xo_open_instance, xo_open_instance_h, xo_open_instance_hd,
     xo_open_instance_d xo_close_instance, xo_close_instance_h,
     xo_close_instance_hd, xo_close_instance_d xo_close_list, xo_close_list_h,
     xo_close_list_hd, xo_close_list_d - open and close lists and instances

LIBRARY
     Text, XML, JSON, and HTML Output Emission Library (libxo, -lxo)

SYNOPSIS
     #include <libxo/xo.h>

     xo_ssize_t
     xo_open_list_h(xo_handle_t *xop, const char *name);

     xo_ssize_t
     xo_open_list(const char *name);

     xo_ssize_t
     xo_open_list_hd(xo_handle_t *xop, const char *name);

     xo_ssize_t
     xo_open_list_d(const char *name);

     xo_ssize_t
     xo_open_instance_h(xo_handle_t *xop, const char *name);

     xo_ssize_t
     xo_open_instance(const char *name);

     xo_ssize_t
     xo_open_instance_hd(xo_handle_t *xop, const char *name);

     xo_ssize_t
     xo_open_instance_d(const char *name);

     xo_ssize_t
     xo_close_instance_h(xo_handle_t *xop, const char *name);

     xo_ssize_t
     xo_close_instance(const char *name);

     xo_ssize_t
     xo_close_instance_hd(xo_handle_t *xop);

     xo_ssize_t
     xo_close_instance_d(void);

     xo_ssize_t
     xo_close_list_h(xo_handle_t *xop, const char *name);

     xo_ssize_t
     xo_close_list(const char *name);

     xo_ssize_t
     xo_close_list_hd(xo_handle_t *xop);

     xo_ssize_t
     xo_close_list_d(void);

DESCRIPTION
     Lists are sequences of instances of homogeneous data objects.  Two
     distinct levels of calls are needed to represent them in our output
     styles.  Calls must be made to open and close a list, and for each
     instance of data in that list, calls must be make to open and close that
     instance.

     The name given to all calls must be identical, and it is strongly
     suggested that the name be singular, not plural, as a matter of style and
     usage expectations.

     A list is a 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:
               xo_open_list("item");

               for (ip = list; ip->i_title; ip++) {
                   xo_open_instance("item");
                   xo_emit("{L:Item} '{:name/%s}':0, ip->i_title);
                   xo_close_instance("item");
               }

               xo_close_list("item");
     Getting the list and instance calls correct is critical to the proper
     generation of XML and JSON data.

               EXAMPLE:
                   xo_open_list("user");
                   for (i = 0; i < num_users; i++) {
                       xo_open_instance("user");
                       xo_emit("{k:name}:{:uid/%u}:{:gid/%u}:{:home}0,
                               pw[i].pw_name, pw[i].pw_uid,
                               pw[i].pw_gid, pw[i].pw_dir);
                       xo_close_instance("user");
                   }
                   xo_close_list("user");
               TEXT:
                   phil:1001:1001:/home/phil
                   pallavi:1002:1002:/home/pallavi
               XML:
                   <user>
                       <name>phil</name>
                       <uid>1001</uid>
                       <gid>1001</gid>
                       <home>/home/phil</home>
                   </user>
                   <user>
                       <name>pallavi</name>
                       <uid>1002</uid>
                       <gid>1002</gid>
                       <home>/home/pallavi</home>
                   </user>
               JSON:
                   user: [
                       {
                           "name": "phil",
                           "uid": 1001,
                           "gid": 1001,
                           "home": "/home/phil",
                       },
                       {
                           "name": "pallavi",
                           "uid": 1002,
                           "gid": 1002,
                           "home": "/home/pallavi",
                       }
                   ]

LEAF LISTS
     In contrast to a list of instances, a "leaf list" is list of simple
     values.  To emit a leaf list, call the xo_emit() function using the ""l""
     modifier:
               for (ip = list; ip->i_title; ip++) {
                   xo_emit("{Lwc:Item}{l:item}0, ip->i_title);
               }

     The name of the field must match the name of the leaf list.

     In JSON, leaf lists are rendered as arrays of values.  In XML, they are
     rendered as multiple leaf elements.
               JSON:
                   "item": "hammer", "nail"
               XML:
                   <item>hammer</item>
                   <item>nail</item>

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>.

FreeBSD 13.1-RELEASE-p6        December 4, 2014        FreeBSD 13.1-RELEASE-p6