Shell script parsing 2 ---- variable

I. general Variables

#/Bin/sh

Num = 2

Echo "this is the $ {num} Nd" # If the shell script language variables are tightly connected to letters, add.

Output result:

Ii. System Variables

$ #: Number of command line parameters for input scripts

$ *: All command line parameter values with spaces between each parameter value

$0: Command itself (shell file name)

$1: The First Command Line Parameter

$2: The second command line parameter

For example:

#/Bin/sh

Echo "Number of vars:" $ #

Echo "values of vars:" $ *

Echo "value of val0:" $0

Echo "value of val1:" $1

Echo "value of val2:" $2

Echo "value of val3:" $3

Echo "value of val4:" $4

Execution result:

Conclusion: The result shows that $0 is indeed the name of the file to be executed, $1, $2... is indeed a parameter passed in by the command line. It is worth noting that when the variable is not assigned a value, the content is blank, for example, $4.