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(bashref.info)Shell Expansions

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Shell Expansions
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   Expansion is performed on the command line after it has been split
into `token's.  There are seven kinds of expansion performed:
   * brace expansion

   * tilde expansion

   * parameter and variable expansion

   * command substitution

   * arithmetic expansion

   * word splitting

   * filename expansion

Brace Expansion

Expansion of expressions within braces.

Tilde Expansion

Expansion of the ~ character.

Shell Parameter Expansion

How Bash expands variables to their values.

Command Substitution

Using the output of a command as an argument.

Arithmetic Expansion

How to use arithmetic in shell expansions.

Process Substitution

A way to write and read to and from a

command.

Word Splitting

How the results of expansion are split into separate

arguments.

Filename Expansion

A shorthand for specifying filenames matching patterns.

Quote Removal

How and when quote characters are removed from

words.

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

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

   Only brace expansion, word splitting, and filename expansion can
change 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 `"$@"' (Note: Special Parameters) and `"${NAME[@]}"'
(Note: Arrays).

   After all expansions, `quote removal' (Note: Quote Removal) is
performed.