The following libraries facilitate working with streams and files.
Boost.IOStreams provides streams that go far beyond what the standard library offers. Boost.IOStreams gives you access to more streams to read and write data from and to many different sources and sinks. In addition, filters enable a variety of operations such as compressing/uncompressing data while reading or writing.
Boost.Filesystem provides access to the filesystem. With Boost.Filesystem you can, for example, copy files or iterate over files in a directory.