CHAPTER 6 Special Unix Features
; command separator
& run the command in the background
&& run the command following this only if the previous command completes successfully, e.g.:
grep string file && cat file
|| run the command following only if the previous command did not complete successfully, e.g.:
grep string file || echo "String not found."
( ) the commands within the parentheses are executed in a subshell. The output of the subshell can be manipulated as above.
' ' literal quotation marks. Don't allow any special meaning to any characters within these quotations.
\ escape the following character (take it literally)
" " regular quotation marks. Allow variable and command substitution with theses quotations (does not disable $ and \ within the string).
'command' take the output of this command and substitute it as an argument(s) on the command line
# everything following until <newline> is a comment
The \ character can also be used to escape the <newline> character so that you can continue a long command on more than one physical line of text.