Perl-04-string functions

1. $ position = index (string, substring, skipchars );

This function returns the position of the substring in the string. If the substring does not exist,-1 is returned. The skipchars parameter is an optional parameter, indicating the number of characters that have been skipped. That is: search from this location;

2. rindex (string, substring, skipchars): The function is similar to index (). The difference is that it starts searching from the right of string;

3. $ Len = length (string): Evaluate the length of the string;

4. $ offset = pos (string): returns the position of the last pattern match;

5. $ substring = substr (string, skipchars, length): This function skips the position of skipchars in string (from the position of skipchars) start to extract the length of the Child string; the first character is 0;

6. Study (string): increases the access speed of variables in an internal format, and takes effect only for one variable at a time;

7. LC (string): converts all letters in string to lowercase letters;

8. UC (string): converts all letters in string to uppercase letters;

9. lcfirst (string): converts the first letter in string to a lower-case letter;

10. ucfirst (string): converts the first letter in the string to a uppercase letter;

11. Join (sepatorstring, list): concatenates all elements in the list to the same string, and separates two adjacent elements using sepatorstring;

12. sprintf (formatstring, field1, field2 ,..., fieldn): this function is used in the same way as the sprintf () function in C language. It is used to format multiple strings. The difference is that the function returns the formatted result string;

13. quotemeta (string): Add a backslash (/) to the front of a non-word in string "/";

14. HEX (string): converts hexadecimal data in the string format to a decimal integer;

15. INT (floatnum): removes the fractional part of the floating point and converts it to an integer;

16. OCT (ocunum): converts string-type octal (0) or hexadecimal (0x) data to a decimal number;

17. ord (char): returns the ASCII value (integer) of the character char );

18. CHR (ascii_value): returns the character corresponding to the integer ascii_value; 0 <= ascii_value <= 255;

19. defined (expr): determines whether an element in a variable, array, or array has been assigned a value. expr is a variable name, array name, or array element; if the value has been defined or assigned, true is returned; otherwise, false is returned;

20. UNDEF (expr): cancels the definition of elements in a variable, array, or array, or even cancels sub-ProgramAnd reclaim the occupied space. The returned value is always an undefined value. This value is equivalent to an empty string, for example, $ retvalue = UNDEF (expr );