Shulou(Shulou.com)06/02 Report--

$0 gets the file name of the currently executed shell script, including the script path if the execution script contains a path

$n gets the nth parameter value of the currently executed shell script, nq1.9, which indicates the filename of the script when n is 0; if n is greater than 9, it is enclosed in curly braces, such as ${10}, followed by arguments separated by spaces

$# get the total number of parameters followed by the currently executed shell script

$* get all parameters passed by the current shell script without quotation marks, which are the same as $@. If you add double quotation marks to $*, such as "$*", all parameters are treated as a single string, which is equivalent to "$1 $2 $3".

$@ gets all parameters passed by the current shell script without quotation marks and is the same as $*: if you add double quotation marks to $@, such as "$@", all parameters are treated as different independent strings, equivalent to "$1"$2"$3"." This is the best way to pass multiple parameters to other programs because it preserves any white space embedded in each parameter. When "$@" and "$*" are enclosed in double quotation marks, there is a difference between them, and there is no difference between them without double quotation marks.

$? Gets the return value of the last instruction executed by the current shell script

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