Perl built-in special Variables

I. Special variables of Regular Expressions:

1. $ N: contains the nth substring of the last pattern match.

2. $ &: String matched in the previous successful mode

3. $ ': Content Before the successful substring

4. $ ': content after the child string that was matched successfully before

5. $ +: the string that was previously matched using the brackets pattern.

Ii. Special variables of the file handle:

1. $ |: if it is set to zero, the fflush function is automatically called every time the function write or print is called, and the written content is written back to the file.

2. $ %: current output page number

3. $ =: current length of each page

4. $-: number of remaining lines on the current page

5. $ ~ : Name of the current report output format. The default value is the file handle name.

6. $ ^: name of the current report output Header Format. The default value is the file handle name with the suffix "_ top.

Iii. Global Special variables:

1. $ _ and $ Arg: Default Input and mode matching content. If you do not specify to receive input variables or strings that match the execution mode

2. $. and $ Nr: current row number of the file handle read before

3. $/and $ RS: the input record delimiter. The default Delimiter is a new line character. If you use the UNDEF variable, it will be read to the end of the file.

4. $, $ OFS: Output domain separator.

5. $ \ and $ ors: Output record Separator

6. $: The line break character. The default value is "\ n -".

7. $! : The numeric value of this variable is the value of errno, and the string value is the corresponding system error string

8. $ @: error message of the command eval. If it is null, the last eval command is successfully executed.

9. $: Process Number of the current Perl script program

10. $ <: actual user number of the current process

11. $>: valid user number of the current process

12. $ (: actual group user number of the current process

13. $): valid group user number of the current process

14. $ [: subscript of the first element of the array. The default value is 0.

15. $]: Perl version

16. $ argv: When "<>" is used to read a file, the current file name is saved.

4. Global Special array variables:

1. @ argv: Save the command line parameters.

2. @ INC: Save and find the directory of the Perl Program

3. @ _: In a subroutine, this array variable contains the parameters passed to the subroutine.

4.% Inc: Hash List % Inc contains all files contained in the do or require statement. The keyword is the file name and the value is the file path.

5.% env: contains the current environment variable

5. Global special file handle

1. argv: traverses the special file handle of all file names in the array variable @ argv

2. stderr: Standard Error output handle

3. stdin: standard input handle

4. stdout: standard output handle

Perl built-in Variables
$-Number of printable lines on the current page, part of the perl format system
$! Returns the error code or string based on the context content.

$ "List Separator

$ # Default digital output format when printing numbers

$ Perl interpreter process ID

$ % Current page number of the current output channel

$ & String matching the previous format

$ (Group ID of the current process

$) Valid group ID of the current process

$ * Setting 1 indicates processing the multiline format. It is replaced by the/s and/M modifiers.

$, Delimiter of the current output field

$. Current row number of the last Read File

$/Delimiter of the current input record. The default value is a new line.

$: Character setting. Subsequent strings are separated to fill continuous fields.

$; Delimiter used to simulate multi-dimensional arrays.

$? Returns the status of the last external command.

$ @ Error message returned by the perl interpreter from the eval statement

$ [Index number of the first element in the array

$ Delimiter of the current output record

$] Sub-version number of the perl interpreter

$ ^ Name of the top page output format of the current channel

$ ^ A variables used to save formatted data before printing

$ ^ D debug flag value

$ ^ E Operating System Extension error message in non-Unix environment

$ ^ F maximum file bundle operator Value

$ ^ H check status of the syntax activated by the compiler

$ ^ I built-in control editor Value

$ ^ L form feed sent to the output channel

$ ^ M backup memory pool size

$ ^ O operating system name

$ ^ P specifies the internal variable of the current debugging Value

$ ^ R result of the last evaluation of the regular expression Block

$ ^ S current interpreter status

$ ^ T start from the new century, and the start time of the notebook is calculated in seconds.

$ ^ W current value of the warning Switch

$ ^ X Perl binary executable code name

$ _ Default input/output and format matching space

$ | Controls the buffer of the currently selected output file handle

$ ~ Name of the current report format

$ 'String before matching information in the previous format

$ 'String after matching information in the previous format

$ + The last parenthesis matching the previous regular expression search format

$ <Real id of the user currently executing the interpreter

$ Contains the matching result in parentheses corresponding to the previous Regular Expression

$ = Number of printable rows on the current page

$> Valid user ID of the current process

$0 contains the file name of the script being executed

$ Argv current file name when reading from the default file handle

% ENV Environment Variable list

% Inc list of files contained through do or require

% Sig signal list and Processing Method

@ _ List of parameters passed to the subroutine

@ Argv: List of command line parameters passed to the script

@ INC: List of directories to be searched during module Import

$-[0] and $ + [0] represent the starting and ending positions of the currently matched Regular Expression in the matched string.