* Info Catalog Prev bash: Shell Parameter Expansion Up bash: Shell Expansions Next bash: Arithmetic Expansion

bash: Command Substitution

 
 3.5.4 Command Substitution
 --------------------------
 
 Command substitution allows the output of a command to replace the
 command itself.  Command substitution occurs when a command is enclosed
 as follows:
      $(COMMAND)
 or
      `COMMAND`
 
 Bash performs the expansion by executing COMMAND in a subshell
 environment and replacing the command substitution with the standard
 output of the command, with any trailing newlines deleted.  Embedded
 newlines are not deleted, but they may be removed during word splitting.
 The command substitution '$(cat FILE)' can be replaced by the equivalent
 but faster '$(< FILE)'.
 
    When the old-style backquote form of substitution is used, backslash
 retains its literal meaning except when followed by '$', '`', or '\'.
 The first backquote not preceded by a backslash terminates the command
 substitution.  When using the '$(COMMAND)' form, all characters between
 the parentheses make up the command; none are treated specially.
 
    Command substitutions may be nested.  To nest when using the
 backquoted form, escape the inner backquotes with backslashes.
 
    If the substitution appears within double quotes, word splitting and
 filename expansion are not performed on the results.
* Info Catalog Prev bash: Shell Parameter Expansion Up bash: Shell Expansions Next bash: Arithmetic Expansion