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June 14, 2006

tips

Find “in use” files and open ports

Posted Jun. 14, ’06, 1:25 PM PT by Dan Moren
Category | Tips

lsofSeveral weeks ago, I discovered a neat trick, thanks to Rob “That’s not a hint; this is a hint” Griffiths. On his Mac OS X Hints weblog, he discussed a terminal command called lsof (short for “list open files”). His suggestion was to use this to find out what application had a file open when you receive this irritating message while trying to empty the Trash: “The operation cannot be completed because the item * is in use.”

If you open up a Terminal session, you can type lsof and it will tell you what files are open. This is usually a pretty long, unhelpful list, but if you add the path and name of the file you’re looking for at the end, for example lsof /Users/dmoren/Desktop/example.txt, it’ll print out just the entry for that file. If you want to see a list of all files open for a particular application, you can pair it with grep, i.e. lsof | grep Safari (the “|” character is the one above your return key; in the command line, it represents a way to take the output of one application and send it into another application).

But that’s not the end of lsof use. Today, I was trying to determine what network port a particular application was using. I did a quick search for solutions on the net, and what should come up, but our old friend lsof? Turns out if you type lsof -i, you’ll get a list of open ports, along with other network info. Piping that through grep makes it pretty easy to find what port you need.


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