First love Perl-File Operations

Putty

Regular Expressions
Review:
@ Array
@ Argv
@ Marr multi-dimensional array

Difference between Su and sudo commands
Http://linux.chinaitlab.com/command/730542_2.html
: WQ is mandatory to write files and exit. Write the file forcibly even if it is not modified, and update the modification time of the file.
 
: X write the file and exit. The file is written only when the file is modified and the file modification time is updated. Otherwise, the file modification time is not updated.

View User Permissions
Http://tech.ddvip.com/2008-01/119991599540175.html

Local declares the global variable e0810.pl. From this we can see thatProgramExecute the function first, and then execute other statements (which can be placed before the function). The function is executed in sequence.
What is the difference between package and module? A module is a set of functions.

Input to perform addition, subtraction, multiplication, division

$ A = <stdin>; $ B = <stdin>;
$ Value1 = add ($ A, $ B );
Print "$ value1 \ n ";
$ Value2 = subtract ($ A, $ B );
Print "$ value2 \ n ";
$ Value3 = mult ($ A, $ B );
Print "$ value3 \ n ";

Sub add {
$ Num1 = shift;
$ Num2 = shift;
Return $ num1 + $ num2;
}
Sub subtract {
$ Num1 = shift;
$ Num2 = shift;
$ Haha = $ num1-$ num2;
Return $ Haha;
}
Sub mult {
$ Num1 = shift;
$ Num2 = shift;
$ Haha = $ num1 * $ num2;
Return $ Haha;
}