I regularly refer to [the unix shell specification][1] to remember the specifics of ${foo%%bar} versus ${foo#bar}, ${parameter:+word} versus ${parameter:-word},

I regularly refer to [the unix shell specification][1] to remember the specifics of ${foo%%bar} versus ${foo#bar}, ${parameter:+word} versus ${parameter:-word}, and so on. It also teaches how && and || work, their relation to [output redirection][3] and [command piping][2], [(...) versus {...}][4], and tricky parts like [word expansion][5], even a full grammar. It's not exciting reading, but it's mostly all there, and works on all POSIXy shells, e.g. sh, bash, ksh, dash, ash, zsh. [1]: https://pubs.opengroup.org/onlinepubs/7908799/xcu/chap2.html https://pubs.opengroup.org/onlinepubs/7908799/xcu/chap2.html [2]: https://pubs.opengroup.org/onlinepubs/7908799/xcu/chap2.html#tag_001_009_002 https://pubs.opengroup.org/onlinepubs/7908799/xcu/chap2.html... [3]: https://pubs.opengroup.org/onlinepubs/7908799/xcu/chap2.html#tag_001_007 https://pubs.opengroup.org/onlinepubs/7908799/xcu/chap2.html... [4]: https://pubs.opengroup.org/onlinepubs/7908799/xcu/chap2.html#tag_001_009_004 https://pubs.opengroup.org/onlinepubs/7908799/xcu/chap2.html... [5]: https://pubs.opengroup.org/onlinepubs/7908799/xcu/chap2.html#tag_001_006 https://pubs.opengroup.org/onlinepubs/7908799/xcu/chap2.html...