If only one could know which skills will be worth learning! The time I invested in learning about APL, Ada, Cobol, RSX/11, Focal, Snobol, 6809 assembler, etc. etc. didn’t return much value beyond amusement, entertainment, and experiance.
Learning all the Unix tools back in 1977 was fun too it has been extremely valuable too!
Sometimes I discover that since then somebody has added a new tool; or a new switch to existing one. Today I learned about the -o switch to grep. It prints out only the matching string; not the whole line.
536$ grep -o '[a-z][a-z]*:[a-z][a-z]*' cascades.rdf | sort | uniq foaf:name my:author my:editor ow:address ow:author ow:booktitle ow:editor ow:institution ow:journal ow:month ...