How do I see current seek position of an open file descriptor?

I'm running an awk script on a 100G+ file. I have a suspicion that since it never finishes it got into some kind of infinite loop.

I want to see the line that script is currently at to see if there's some problem with the data.

I tried ls -l /proc/<pid>/fd but it just lists names of opened files.

Is there a way to find the current seek position of an open file?

Found general solution for Linux (since 2.6.22).

1. Prerequisites: need to find out the process ID (using ps or its equivalent) and the number of the file descriptor of interest (look in /proc/<pid>/fd);
2. Getting the current offset position, in bytes:

   grep pos: /proc/<pid>/fdinfo/<fd>
   # pos:    892141568
   

There is also a useful pv tool that has a mode for interactively displaying the offset of an already open file:

pv -d <pid>:<fd>
# 1,10GiB 0:00:01 [1,10GiB/s] [=======================>      ] 81% ETA 0:05:46

Links:

• lwn.net: add file position info to proc;
• Unix&Linux: How to find out the file offset of an opened file?.
• progress - another tool showing progress for cp, mv, dd, ...;