check dependencies

ldd /path/to/libsomething.so

# at runtime (which processes are using the library)
lsof | grep libsomething.so

# static inspection of ELF headers for a binary
readelf -d /path/to/binary | grep NEEDED
# or
ldd /path/to/binary | grep something

# “-lsomething” flag links with libsomething.so
g++ main.cpp -lsomething

find library

search for the actual .so file of a library

ldconfig -p | grep libsomething