How to find all shared libraries actually used during execution in Linux?

I have an executable and I would like to find out which shared libraries were actually used during a specific run. I know ldd would list all the shared library dependencies of that executable but I would like to find out the subset of those that were actually used during a specific run*. Is this possible?

*what I mean with specific run is running the executable with certain input parameters that would cause only a small part of the code to be run.

Answer

You can use ltrace(1) for this:

$ PROG='ls -l'
# Collect call info
$ ltrace -o calls.txt -l '*' $PROG &> /dev/null
# Analyze collected data
$ cat calls.txt | sed -ne '/->/{ s/^(.*)->.*/1/; p }' | sort -u
libacl.so.1
libcap.so.2
libc.so.6
libselinux.so.1
ls
# Compare with ldd
$ ldd /bin/ls | wc -l
10