Redirecting output from launchd?

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Level 2

217 points

Redirecting output from launchd?

I'm in the process of converting my existing cron tasks over to launchd and encountering a small-ish annoyance. I've gotten into the habit of writing cron commands like this, appending the output to a log file:

some_command and aparameter >> /the/full/path/to/the/logfile.txt

This just gives me a quick-and-dirty way to log activity from cron commands. When I do that in launchd, it doesn't go the expected location, but rather gets written out to the system log. Does launchd not support >> redirection like that or do I need to do it in some other way?

Mac OS X (10.5.5)

Posted on Nov 3, 2008 10:27 PM

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Answer 1

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orangekay

Level 5

4,085 points

Nov 3, 2008 10:38 PM in response to Rick Anderson

You can't shove an entire shell script in a launchd plist, you run one thing with one set of arguments--no piping, no expansion, no redirection. If you want to write to a log file then that code will have to live in whatever it is you want launchd to run.

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Answer 2

Rick Anderson Author

Level 2

217 points

Nov 4, 2008 12:11 AM in response to orangekay

Darn. Not the answer I wanted to hear but helpful nonetheless. Thank you.

I suppose the cleanest way to move some of my existing cron entries over would be by dropping them into a shell script and running that in launchd.

Message was edited by: Rick Anderson

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Answer 3

Camelot

Level 9

54,333 points

Nov 4, 2008 10:28 AM in response to Rick Anderson

If you want to write to a log file then that code will have to live in whatever it is you want launchd to run

Orange isn't actually correct here (sorry, Orange).

The solution actually lies in the .plist file for your script. launchd has many, many keys it supports one of which is:

StandardOutPath <string>
This optional key specifies what file should be used for data being sent
to stdout when using stdio(3).

Therefore your solution is to add a StandardOutPath key to your .plist

man launchd.plist lists all the keys that launchd uses.

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Answer 4

orangekay

Level 5

4,085 points

Nov 4, 2008 11:04 AM in response to Camelot

Yup, that will work if you want all of stdout written there. Just can't treat launchd like a login shell.

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Answer 5

Camelot

Level 9

54,333 points

Nov 4, 2008 12:30 PM in response to orangekay

Yup, that will work if you want all of stdout written there. Just can't treat launchd like a login shell.

OK, I guess we read the OP differently - I was focussing on the desire to capture stdout. No biggie 🙂

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Answer 6

Rick Anderson Author

Level 2

217 points

Nov 4, 2008 3:18 PM in response to Camelot

Great! Thanks. I'm a bit of a launchd noob and these posts help me understand it much better.

I've looked around on the web for a good run-down of what it can do and some examples, but found very little. Seems like a great tool. I'm surprised there aren't more examples and tutorials out there showing what it can do.

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Answer 7

Tony T1

Level 6

10,232 points

Nov 6, 2008 6:50 PM in response to Rick Anderson

An excellent gui shell is lingon http://tuppis.com/lingon/
Apple Tutorial: Getting Started with launchd http://developer.apple.com/macosx/launchd.html
launchd in Depth: http://www.afp548.com/article.php?story=20050620071558293
launchd: One Programm to Rule Them All – Video presentation of launchd: http://video.google.com/videoplay?docid=1781045834610400422

I've looked around on the web for a good run-down of what it can do and some examples, but found very little. Seems like a great tool. I'm surprised there aren't more examples and tutorials out there showing what it can do.

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Answer 8

Rick Anderson Author

Level 2

217 points

Nov 14, 2008 2:44 AM in response to Tony T1

Thanks. I appreciate the links.

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