Marc Rochkind used to recommend reading the entire UNIX manual each year. That was good advice in the late 70's, but it would be hopelessly impractical now, quite beyond the lack of a manual to read. There are just too many commands and libraries. A valuable service would be to identify the most useful tools. Those in the old manuals would be an interesting starting point, but I can't remember when I last used "ar" command, which I mostly used to pack multiple files into a single one to save inodes and wasted file system space, neither of which matter any more. If there were a corpus of contemporary shell scripts, identifying the most used commands could be interesting. Perl's CPAN (comprehensive perl archive network) could be a corpus of scripts from which the most commonly used system calls could be extracted.