deb-shlibs man page
deb-shlibs — Debian shared library information file
shlibs files map shared library names and versions (sonames) to dependencies suitable for a package control file. There is one entry per line. Blank lines are not allowed. Lines beginning with an # character are considered commentary, and are ignored. All other lines must have the format
[type:] library version dependencies
The library and version fields are whitespace-delimited, but the dependencies field extends to the end of the line. The type field is optional and normally not needed.
The dependencies field has the same syntax as the Depends field in a binary control file, see deb-control(5).
The shlibs file for a typical library package, named libcrunch1, that provides one library whose soname is libcrunch.so.1, might read
libcrunch 1 libcrunch1 (>= 1.2-1)
The dependencies must mention the most recent version of the package that added new symbols to the library: in the above example, new symbols were added to version 1.2 of libcrunch. This is not the only reason the dependencies might need to be tightened.
deb-control(5), dpkg-shlibdeps(1), deb-symbols(5).