Expansion (zsh)

## 14 Expansion ¶

The following types of expansions are performed in the indicated order in five steps:

History Expansion

  This is performed only in interactive shells.

Alias Expansion

  Aliases are expanded immediately before the command line is parsed as explained in Aliasing.

Process Substitution
Parameter Expansion
Command Substitution
Arithmetic Expansion
Brace Expansion

  These five are performed in left-to-right fashion. On each argument, any of the five steps that are needed are performed one after the other. Hence, for example, all the parts of parameter expansion are completed before command substitution is started. After these expansions, all unquoted occurrences of the characters ‘`\`’,‘`'`’ and ‘`"`’ are removed.

Filename Expansion

  If the `SH_FILE_EXPANSION` option is set, the order of expansion is modified for compatibility with sh and ksh. In that case filename expansion is performed immediately after alias expansion, preceding the set of five expansions mentioned above.

Filename Generation ¶

  This expansion, commonly referred to as globbing, is always done last.

The following sections explain the types of expansion in detail.