I have done a listing of the device folder two times, one time without the sd-card in the slot and one time inserted, the system automatically adds one file in the device folder.

$ ls /dev | wc -l
$ ls /dev | wc -l

I could put each listing into a separate file: ls /dev > foo. But how can I determine from this point the device file that was added?


You could run this before adding the device to store the inital list in a file:

ls /dev >~/a

And then this after adding the device:

ls /dev | diff -u ~/a -

This should show you in what way the two lists of files differ. diff shows the differences between two text files, and flag -u changes its output format: lines added will be prefixed with a + sign. For example, if you get the following output (I omitted the diff header):


then it means that the new device that got created is /dev/sdf.

You can then delete the temporary file ~/a.

Another way to get the information you are looking for would be to tail -f /var/log/messages: you should see kernel messages mentioning the new device's appearance and disappearance.

  • a is here just another name for the file like foo, right ? – Abdul Al Hazred Mar 20 '15 at 18:53
  • Yes, you can call the file anything you like, as long as you use the same name in both commands. – dhag Mar 20 '15 at 19:00
  • I do not understand this diff command and the -u option at all, but I opened a new question about it. – Abdul Al Hazred Mar 20 '15 at 19:02
  • I will edit my answer to explain this use of diff. – dhag Mar 20 '15 at 19:04

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