My problem is that with lsof -p pid I can find out the list of opened file of a process whose process id is pid. But is there a way to find out the file offset of each accessed file ?

Please give me some suggestions ?


On linux, you can find the position of the file descriptor number N of process PID in /proc/$PID/fdinfo/$N. Example:

$ cat /proc/687705/fdinfo/36
pos:    26088
flags:  0100001

The same file can be opened several times with different positions using several file descriptors, so you'll have to choose the relevant one in the case there are more than one. Use:

$ readlink /proc/$PID/fd/$N

to know what is the file to which the corresponding file descriptor is attached (it might not be a file, in this case the symlink is dangling).

  • 4
    Your answer is great. – Ta Thanh Dinh Mar 22 '12 at 16:18
  • I strongly agree! – eftshift0 Sep 23 '20 at 15:17

lsof can do this, with the -o option.

Under Linux, it gets its information from /proc, so you can get it there as well.

  • It has been a long time since my last question, and I have not been here for a long time. Thank you for the answer. – Ta Thanh Dinh Apr 18 '12 at 9:21
  • 1
    I can confirm this works as well. The offset is given as HEX, though. – BenMorel Mar 13 '18 at 23:44

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