Re: How to detect X?

[Zaxo]

You could simply try the X version first. If the X server fails to appear, exec returns with an error -- the only way exec can return. Then try the command-line version.

exec "$bin/$name.X", @args;
exec "$bin/$name.cmd", @args;

[blazar]

You could simply try the X version first. If the X server fails to appear, exec returns with an error -- the only way exec can return. Then try the command-line version.

This is fundamentally what I had thought of doing myself, even though, really I was rather thinking of putting some minimal Tk code in an eval block instead. Yes: I know that basically that would mean doing the same thing twice, but it seems somewhat cleaner... of course unless there's an even cleaner solution.

[Anonymous Monk]

No, that doesn't work. From the manual page:

It [exec] fails and returns false only if the command does not exist and it is executed directly instead of via your system's command shell (see below).

Since in this case "$bin/$name.X" must exist, the exec will succeed. The fact that "$bin/$name.X" can't do its job doesn't mean the exec will magically resurrect the program.

In fact, if you turn warnings on, the lines you give above will generate a warning:

Since it's a common mistake to use "exec" instead of "system", Perl warns you if there is a following statement which isn't "die", "warn", or "exit" (if "-w" is set - but you always do that).