Assuming the language provides it, what are some things to do or libraries to use that every programmer should know?
My list would be
- Regular Expressions
- Named Pipes
- standard IO (std in/out/error)
- Executing outside executables (like imagemagik and your own scripts)
- How to grab an HTTP page as a string (mostly for updates and grabbing configs from servers)
I have a similar questions about tools. Also I am looking for specific answers. I don't want answers that can be done in different ways (such as learn how to synchronize threads).
I know how to do the above in 3+ languages. There always seems to be things programmers don't know how to do which can make their lives easier. For a long time I didn't know what regular expression was (although I did hear of it) and I was surprised how many people who tried to make a toolchain or complex app and did not know how to (or that you could) get the stdout from an exe they launched (they checked for errors in a very weird way or just didn't and hope it produce the expected results).
What do you think is useful, not well known and should be something every senior (or starting out) programmer should know?