[launchd-dev] General questions on launchd

[Damien Sorresso]

On Jun 1, 2009, at 12:17 PM, Scott Haneda wrote:
> Thanks for all the data, very helpful.  So let me test case this, as  
> I still have issues, on the most basic of a test.
>
> On Jun 1, 2009, at 11:58 AM, Damien Sorresso wrote:
>
>> On Jun 1, 2009, at 11:29 AM, Scott Haneda wrote:
>>> Hello, first post, I have done my best to hit up nabble archives  
>>> and see if there are any answers, so far, no luck.  I am on 10.5.
>>>
>>> Where does one draw the line from stuffing a command into a plist  
>>> versus having a simple command call a more complicated script,  
>>> even if the script to be called is not that complicated?
>>>
>>> Example:
>>> <dict>
>>> 	<key>ProgramArguments</key>
>>> 	<array>
>>> 		<string>/bin/bash /Users/me/Library/Application\ Support/dir/ 
>>> script</string>
>>> 	</array>
>>> </dict>
>>> </plist>
>>>
>> The structure of ProgramArguments dictates that you specify one  
>> argument per array element. While what you have works, it's only  
>> because the shell you're targeting understands it. In other words,  
>> don't get in the habit. It's a one-time cost to structure your  
>> plist appropriately, and Property List Editor makes it easy.
>
> My bad, sorry, that was a hand typed example, and I would have  
> usually put arg/array correctly.
>
>>> * How important is it to use full paths to binaries like `echo`  
>>> and `ls`, as long as I am sure that I have not mucked with the  
>>> environment variables to them?  Are environment variables cleared  
>>> in launchd, or do user launchd plists need to have care taken to  
>>> make sure an alias bash alias will get in the way?
>>>
>>> I have never been able to get that to work.  syslog tells me
>>> Jun  1 11:02:47 host com.apple.launchd[155] (com.me.foo[19809]):  
>>> posix_spawnp("/Users/me/Library/Application Support/dir/ 
>>> script", ...): No such file or directory
>>> Jun  1 11:02:47 host com.apple.launchd[155] (com.me.ALARM[19809]):  
>>> Exited with exit code: 1
>>
>> launchd uses posix_spawn(2), which will search _PATH_DEFPATH, which  
>> is specified as "/usr/bin:/bin". Personally, I try to always use  
>> the full path to an executable. It's just good practice.
>
> Ok, thank you, test case so far is:
> $cat ~/Library/Application\ Support/launchd-test/tester
> #!/bin/bash
> echo `date` >> /Users/me/Desktop/launchdtest.txt
> echo "this is working" >> /Users/me/Desktop/launchdtest.txt
>
> ./tester
> $cat ~/Desktop/launchdtest.txt
> Mon Jun 1 12:07:41 PDT 2009
> this is working
>
> It works, run interactively at least.  I make a launchd item for it.
> Stored in ~/Library/LaunchAgents/
> -rw-r--r--  1 me  staff  479 Jun  1 12:11 com.me.test.foo.plist
>
> <?xml version="1.0" encoding="UTF-8"?>
> <!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs 
> /PropertyList-1.0.$
> <plist version="1.0">
> <dict>
>        <key>Label</key>
>        <string>com.me.test.foo</string>
>        <key>ProgramArguments</key>
>        <array>
>                <string>/bin/bash</string>
>                <string>/Users/me/Library/Application\ Support/ 
> launchd-test/tester</string>
>        </array>
>        <key>RunAtLoad</key>
>        <true/>
>        <key>StartInterval</key>
>        <integer>10</integer>
> </dict>
> </plist>
>
> Now, tail the log file, nothing, look at the syslog, every 10 seconds:
> Jun  1 12:15:11 macbook com.me.test.foo[1010]: /bin/bash: /Users/me/ 
> Library/Application\ Support/launchd-test/tester: No such file or  
> directory
> Jun  1 12:15:11 macbook com.apple.launchd[123] (com.me.test.foo 
> [1010]): Exited with exit code: 127
>
> I will look into the "WorkingDirectory" now, but I am stumped as to  
> why this should not work as is.  Thanks again for the pointers.


You're still escaping the space in "Application Support"  
unnecessarily. launchd is not a shell interpreter, and the contents of  
each element of ProgramArgument is passed directly to posix_spawn(2),  
so you don't need to escape anything. Use this instead:

> <?xml version="1.0" encoding="UTF-8"?>
> <!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs 
> /PropertyList-1.0.$
> <plist version="1.0">
> <dict>
>        <key>Label</key>
>        <string>com.me.test.foo</string>
>        <key>ProgramArguments</key>
>        <array>
>                <string>/bin/bash</string>
>                <string>/Users/me/Library/Application Support/launchd- 
> test/tester</string>
>        </array>
>        <key>RunAtLoad</key>
>        <true/>
>        <key>StartInterval</key>
>        <integer>10</integer>
> </dict>
> </plist>
-- 
Damien Sorresso
BSD Engineering
Apple Inc.

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