XML Output: libxo - provide single API to output TXT, XML, JSON and HTML

[Phil Shafer]

"Simon J. Gerraty" writes:
>w(1) sizes those strings based on its expectation of the width of the
>tty.  That can obviously be fixed/improved - but involves exposing
>knowledge of the out format (or at least that it isn't TXT) to the
>application. 

libxo allows the field description to carry two distinct format
descriptors, one for text/html and one for xml/json.  The latter
defaults to the former:

    xo_emit(" {:words/%7ju/%ju}", twordct);

For "w", this is does the right thing; in text mode, the command
string is truncated:

 5:08AM  up 27 days, 12:22, 11 user%s, load averages: 0.00, 0.00, 0.00
USER             TTY      FROM              LOGIN@  IDLE WHAT
phil             pts/1    76.182.32.73     05Jul14     - /usr/bin/perl /u/phil/bin/plum (
...

In XML mode, the command is not truncated.

<uptime-information>
  <time-of-day> 5:09AM</time-of-day>
  <uptime seconds="2377336">27 days</uptime>
  <uptime>12:22</uptime>
  <users>11</users>
  <load-average-1>0.00</load-average-1>
  <load-average-5>0.00</load-average-5>
  <load-average-15>0.00</load-average-15>
  <user-table>
    <user-entry>
      <user>phil</user>
      <tty>pts/1</tty>
      <from>76.182.32.73</from>
      <login-time>05Jul14</login-time>
      <idle> 1</idle>
      <command>/usr/bin/perl /u/phil/bin/plum (perl5.12.4)</command>
    </user-entry>
...

(Yes, I'm likely the only plum user left in the wild.)

Thanks,
 Phil