Name for ${...} constructs (for strings and arrays) in bash?

Question

Bash allows things like ${#string} (string length) or ${array[10]} (indexing array). There's many more forms than the above, for example ones for trimming, replacing, changing case, etc.

I've been unable to find a proper name for these. I've seen sources refer to these as "string manipulations" or "array manipulations", but I can't find any official source using these names.

The manual seems to do it's best to avoid naming these constructs at all.

Does anyone know a name for these sorts of constructs? (ones of the form ${....} used to manipulate strings and arrays.) Or at least an unofficial name I could Google?

Answer 1

These are "parameter expansion" constructs.

See:

• https://wiki.bash-hackers.org/syntax/pe (the relevant page in the bash-hackers' wiki)
• https://pubs.opengroup.org/onlinepubs/9699919799/utilities/V3_chap02.html#tag_18_06_02 (the relevant section of the POSIX sh specification)
• https://www.gnu.org/software/bash/manual/bash.html#Shell-Parameter-Expansion (the official manual)