Citation :
Command Substitution
Command substitution allows the output of a command to replace the command name. There are
two forms:
$(command)
or
‘command‘
Bash performs the expansion by executing command and replacing the command substitution
with the standard output of the command, with any trailing newlines deleted. Embedded new‐
lines are not deleted, but they may be removed during word splitting. The command substi‐
tution $(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 back‐
slash 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 pathname expansion are
not performed on the results.
|