科技回声

3 条评论

fensipens超过 10 年前

Sorry Pädu but this smells for many reasons.. first:<pre><code> The dns-sd command is primarily intended for interactive use. Because its command-line arguments and output format are subject to change, invoking it from a shell script will generally be fragile. Additionally, the asynchronous nature of DNS Service Discovery does not lend itself easily to script-oriented programming. For example, calls like "browse" never complete; </code></pre> Second, "SIGKILL is too verbose, SIGINT is too soft".. how about SIGTERM? Its very likely that you're doing it wrong if you need to use -KILL in your scripts.Third, "[1] 58181 killed ./discover-vnc.sh --- It's crucial to suppress this line." again, if you think you must suppress this, you're doing it wrong. This shouldn't pop up in the first place.Fourth, what about fifos and `$!'?Fifth, why bash? Use the sh-subset.etc.It's cute that you managed to solve your problem but this is nothing more than an unreliable hack, pompously presented ("Taming non-terminating Bash processes", "Kill the children"..)

评论 #8578139 未加载

ttwwmm超过 10 年前

The use of <(..) is really weird here... why not just pipe dns-sd to the while loop?<pre><code> dns-sd | while read -r line ; do ... done </code></pre> Sure, you won't be able to accumulate the output for the trap, but you shouldn't need to---this is stream processing!Consider replacing the while loop with awk. This sort of thing is exactly what awk is good at:<pre><code> BEGIN { FS = " "; count = 0; } NR > 5 { count++ print if ($3 != "3") { exit; } } END { printf("%d hosts found\n", count); } </code></pre> You could also do it with GNU sed (you'll need the q or Q command for early exit, and that's a GNU extension---no idea if it's available on OS X).

评论 #8578202 未加载

fragmede超过 10 年前

That's all well and good, but the real issue is that dns-sd is really meant to be used from a shell script.It should be noted that Linux's command line program to enumerate network services, avahi-browse, includes a '-t' flag so that terminates after dumping service entries.<a href="https://developer.apple.com/library/mac/documentation/Darwin/Reference/ManPages/man1/dns-sd.1.html" rel="nofollow">https://developer.apple.com/library/mac/documentation/Darwin...</a>