Shell Expansions

Expansion is performed on the command line after it has been split into tokens. Bash performs these expansions:

brace expansion
tilde expansion
parameter and variable expansion
command substitution
arithmetic expansion
word splitting
filename expansion
quote removal

The order of expansions is: brace expansion; tilde expansion, parameter and variable expansion, arithmetic expansion, and command substitution (done in a left-to-right fashion); word splitting; filename expansion; and quote removal.

On systems that can support it, there is an additional expansion available: process substitution. This is performed at the same time as tilde, parameter, variable, and arithmetic expansion and command substitution.

Quote removal is always performed last. It removes quote characters present in the original word, not ones resulting from one of the other expansions, unless they have been quoted themselves. See Quote Removal for more details.

Only brace expansion, word splitting, and filename expansion can increase the number of words of the expansion; other expansions expand a single word to a single word. The only exceptions to this are the expansions of "$@" and $* (see Special Parameters), and "${name[@]}" and ${name[*]} (see Arrays).