Lots of applications will fail,
Really? For years, I would set $ENV{DISPLAY} in my profile (so if I would telnet/rsh/rlogin to another box, things would display at my screen - and if I started X somewhere else, DISPLAY would be reset). Yet, I would never had an application fail because of that.

See, if you don't have X running, X applications will fail. Not because $ENV{DISPLAY} is set, but because X isn't running. Non X-application don't give a shit about $ENV{DISPLAY}. The only thing that could "fail" is an X-application displaying on the wrong screen - but that would only happen if the environment had not setup $ENV{DISPLAY} - and then it would use a default variable instead of being undefined. Ho hum.

Using DISPLAY is just the convention with X.
Indeed. The fallacy in your reasoning is that there's also a convention about DISPLAY (namely, it being unset) in a non-X environment. Unfortunally, that isn't true.

In reply to Re^2: How to detect X? by Anonymous Monk
in thread How to detect X? by blazar

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.