An italic page number such as 123 indictes a definition. A light page number such as 456 indicates a brief mention. Page numbers followed by the letter t refer to tables. Only variables that must always appear with a leading dollar sign are indexed with a leading dollar sign. Other variables are indexed without a leading dollar sign.
! (NOT) Boolean operator 468, 574
!! reexecutes the previous event 313
# comment 756
#! specifies a script shell 280, 407
$ bash
parameters 438–443
$ in regular expressions 890
$ in variable names 292
$ prompt 27
$! parameter 440
$# parameter 441
$#argv variable 372
$$ variable 376
$((...)) see arithmetic, expansion
$(...)
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