Using ASObjC Runner to abort a shell script command in Applescript - shell

Question

I've got ASObjC Runner code in my AppleScript that shows a progress window once a do shell script is run. How do I make the button on the progress window kill the shell script?
Heres a sampling of my code:
tell application "ASObjC Runner"
reset progress
set properties of progress window to {button title:"Abort", button visible:true, indeterminate:true}
activate
show progress
end tell
set shellOut to do shell script "blahblahblah"
display dialog shellOut
tell application "ASObjC Runner" to hide progress
tell application "ASObjC Runner" to quit

Answer 1

There are several parts to the answer:
Asynchronous do shell script: normally, do shell script only returns after the shell command has completed, which means you cannot act on the processes inside the shell. However, you can get a do shell script command to execute asynchronously by backgrounding the shell command it executes, i.e.
do shell script "some_command &> /target/output &"
– which will return immediately after launching the shell command. As it will not return the command’s output, you have to catch that yourself, for instance in a file (or redirect to /dev/null if you don’t need it). If you append echo $! to the command, do shell script will return the PID of the background process. Basically, do
set thePID to do shell script "some_command &> /target/output & echo $!"
see Apple’s Technical Note TN2065. Stopping that process is then a simple matter of doing do shell script "kill " & thePID.
Hooking into ASObjC Runner’s progress dialog is just a matter of polling its button was pressed property and breaking on true:
repeat until (button was pressed of progress window)
delay 0.5
end repeat
if (button was pressed of progress window) then do shell script "kill " & thePID
Deciding when your shell script is done to dismiss the progress dialog: that is the interesting part, as the shell command operates asynchronously. Your best bet is to shell out to ps with the PID you retrieved to check if the process is still running, i.e.
if (do shell script "ps -o comm= -p " & thePID & "; exit 0") is ""
will return true when the process is not running anymore.
Which leaves you with the following code:
tell application "ASObjC Runner"
reset progress
set properties of progress window to {button title:"Abort", button visible:true, indeterminate:true}
activate
show progress
try -- so we can cancel the dialog display on error
set thePID to do shell script "blahblahblah &> /file/descriptor & echo $!"
repeat until (button was pressed of progress window)
tell me to if (do shell script "ps -o comm= -p " & thePID & "; exit 0") is "" then exit repeat
delay 0.5 -- higher values will make dismissing the dialog less responsive
end repeat
if (button was pressed of progress window) then tell me to do shell script "kill " & thePID
end try
hide progress
quit
end tell
If you need to capture the output of your background shell command, you will have to redirect it to file and read out that file’s content when done, as noted above.