s6-portable-utils is a set of tiny general Unix utilities, often performing well-known tasks such as cut and grep, but optimized for simplicity and small size. They were designed for embedded systems and other constrained environments, but work everywhere. Other sets of small utilities are usually system-specific; for instance, the (otherwise excellent) BusyBox project only works on Linux.
Xidel is a command line tool to download Web pages and extract data from them. It can download files over HTTP/S connections, follow redirections, links, or extracted values, and process local files. The data can be extracted using XPath 2.0, XQuery 1.0, and JSONiq expressions, CSS 3 selectors, and custom, pattern-matching templates that are like an annotated version of the processed page. The extracted values can then be exported as plain text/XML/HTML/JSON, or assigned to variables to be used in other extract expressions or be exported to the shell. There is also an online CGI service for testing.