Finding change in shared object through bash

Question

Here's my case- I have a package named say foo-1.2.3. I want to know which package it installs. So, I install it in a fakeroot approach and make a list of all files it install in a file called FILES

Suppose I want to upgrade it to foo-1.2.4. In the same way, I created the FILES file for it. I know that if the name of the shared library changes, all the packages dynamically linked to it needs to be re-compiled. So I want to write a bash script which will notify me.

For example, say the old FILES contains-

/usr/lib/libfoo.so.1
/usr/lib/libfooabc.so.1
/usr/lib/something.so.1
/usr/share/doc/foo-1.2.3/whatever

And let's say the new FILES contains-

/usr/lib/libfoo.so.2
/usr/lib/libfooabc.so.2
/usr/lib/something.so.1
/usr/share/doc/foo-1.2.4/whatever

I want the script to notify me that, /usr/lib/libfoo.so.1 and /usr/lib/libfooabc.so.1 have changed.

I tried this

grep -F -x -f old new|grep -E *\.so\.*

But it doesn't work as expected when the file old is-

/usr/lib/libfooabc.so.1
/usr/lib/libfoo.so.1
/usr/lib/libfoo.so.2
/usr/lib/something.so.1
/usr/share/doc/foo-1.2.3/whatever

And new is-

/usr/lib/libfoo.so.2
/usr/lib/libfoo.so.3
/usr/lib/libfooabc.so.2
/usr/lib/something.so.1
/usr/share/doc/foo-1.2.4/whatever

The output is-

/usr/lib/libfoo.so.2
/usr/lib/something.so.1

The desired output is-

/usr/lib/libfooabc.so.1
/usr/lib/libfoo.so.1

Answer 1

I came up with two options using diff that should work for you.

Using diff -u and sed:

diff -u old new | sed  -n 's/^-\(.*\.so\..*\)/\1/p'
/usr/lib/libfoo.so.1
/usr/lib/libfooabc.so.1

• That command outputs the full diff between the two files, and we use sed to filter out only the changes from the 'old' file (indicated by a leading -), and further filter on the diff containing .so.. To strip out the - from the diff output we use a backreference to print everything but that.

Using diff output formatting and grep

Two variants on the same thing; the second one is shorter, they both behave identically to each other and the previous example.

diff --old-line-format='%L' --unchanged-line-format= --new-line-format= old new | grep '\.so\.'

or slightly better:

diff --changed-group-format='%<' --unchanged-line-format=  old new | grep '\.so\.'

You may be able to get diff to do the job entirely by itself - it does have regex filtering (-I ignore flag), but it behaves oddly when you need to invert the regex. I've never had much luck with it.