3 ms·

Sorry Pädu but this smells for many reasons.. first: The dns-sd command is primarily intended for interactive use. Because its command-line argument

Sorry Pädu but this smells for many reasons.. first: 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; 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"..)

pstadler 12y ago
Thanks man, your feedback is appreciated. I'm well aware of the dirty nature of this solution[1] but it seems to be the only way to achieve this within context (OS X, Alfred). [1] https://github.com/pstadler/non-terminating-bash-processes#conclusion https://github.com/pstadler/non-terminating-bash-processes#c... Edit: $! is not working with the distributed Bash version (currently 3.2) on OS X. Unfortunately, dns-sd is the only utility to discover network services on OS X. There are many projects which use the same hack involving dns-sd. I invite you to find a better solution to this problem.
- fensipens 12y ago
  Try something like this (untested): #! /bin/sh fifo=/tmp/discover-vnc.fifo rm -f $fifo mkfifo $fifo dns-sd -B _rfb._tcp >$fifo & pid=$! while read line; do case $line in *_rfb._tcp.*) # do something here.. then test # if flag=3 and break otherwise esac done <$fifo kill $pid
  - pstadler 12y ago
    Results from dns-sd are not necessarily being delivered instantly and there might be no lines which contain this flag to check of it's the last entry. It's also rather ugly to create a named pipe for this purpose, don't you think?
    - fensipens 12y ago
      there might be no lines which contain this flag Again, untested: #! /bin/sh timeout=5 fifo=/tmp/discover-vnc.fifo rm -f $fifo mkfifo $fifo dns-sd -B _rfb._tcp >$fifo & pid1=$! while read line; do case $line in *_rfb._tcp.*) # do something here.. then test # if flag=3 and break otherwise esac done <$fifo & pid2=$! sleep $timeout && kill $pid1 $pid2 & pid3=$! wait $pid2 kill $pid3 It's also rather ugly to create a named pipe for this purpose Because it creates a file in /tmp? Who cares? The alternative is bash voodoo magic.. the same magic that gave us shellshock.
      - pstadler 12y ago
        The alternative is bash voodoo magic.. the same magic that gave us shellshock. I love this one.
- fensipens 12y ago
  $! is not working with the distributed Bash version (currently 3.2) on OS X. $ bash --version GNU bash, version 3.2.48(1)-release (x86_64-apple-darwin10.0) Copyright (C) 2007 Free Software Foundation, Inc. $ : & echo $! [1] 329 329
  - pstadler 12y ago
    $BASHPID is not working with subshells prior to Bash v4.
    - fensipens 12y ago
      $BASHPID and $! are two different things.
      - pstadler 12y ago
        I need to know the PID of the subshell, inside the subshell. $BASHPID was introduced to hold this value. While $$ still contains the PID of the parent process and $! is not available inside the subshell after all.

pstadler 12y ago

Thanks man, your feedback is appreciated. I'm well aware of the dirty nature of this solution[1] but it seems to be the only way to achieve this within context (OS X, Alfred). [1] https://github.com/pstadler/non-terminating-bash-processes#conclusion https://github.com/pstadler/non-terminating-bash-processes#c... Edit: $! is not working with the distributed Bash version (currently 3.2) on OS X. Unfortunately, dns-sd is the only utility to discover network services on OS X. There are many projects which use the same hack involving dns-sd. I invite you to find a better solution to this problem.

fensipens 12y ago
Try something like this (untested): #! /bin/sh fifo=/tmp/discover-vnc.fifo rm -f $fifo mkfifo $fifo dns-sd -B _rfb._tcp >$fifo & pid=$! while read line; do case $line in *_rfb._tcp.*) # do something here.. then test # if flag=3 and break otherwise esac done <$fifo kill $pid
- pstadler 12y ago
  Results from dns-sd are not necessarily being delivered instantly and there might be no lines which contain this flag to check of it's the last entry. It's also rather ugly to create a named pipe for this purpose, don't you think?
  - fensipens 12y ago
    there might be no lines which contain this flag Again, untested: #! /bin/sh timeout=5 fifo=/tmp/discover-vnc.fifo rm -f $fifo mkfifo $fifo dns-sd -B _rfb._tcp >$fifo & pid1=$! while read line; do case $line in *_rfb._tcp.*) # do something here.. then test # if flag=3 and break otherwise esac done <$fifo & pid2=$! sleep $timeout && kill $pid1 $pid2 & pid3=$! wait $pid2 kill $pid3 It's also rather ugly to create a named pipe for this purpose Because it creates a file in /tmp? Who cares? The alternative is bash voodoo magic.. the same magic that gave us shellshock.
    - pstadler 12y ago
      The alternative is bash voodoo magic.. the same magic that gave us shellshock. I love this one.
fensipens 12y ago
$! is not working with the distributed Bash version (currently 3.2) on OS X. $ bash --version GNU bash, version 3.2.48(1)-release (x86_64-apple-darwin10.0) Copyright (C) 2007 Free Software Foundation, Inc. $ : & echo $! [1] 329 329
- pstadler 12y ago
  $BASHPID is not working with subshells prior to Bash v4.
  - fensipens 12y ago
    $BASHPID and $! are two different things.
    - pstadler 12y ago
      I need to know the PID of the subshell, inside the subshell. $BASHPID was introduced to hold this value. While $$ still contains the PID of the parent process and $! is not available inside the subshell after all.