Perl string and sorting

Index (primary string, substring) starts from 0 and returns the position of the most recent substring in the primary string.

Rindex (Main string, sub-string) Searches from the end and returns the position of the most recent sub-string in the main string.

You can accept the third parameter, indicating that the user starts searching. The default value is from 0 or the last

Substr operation substring

Three parameters: a string, an initial value from scratch, and the length of the sub-string returned value is a sub-string

If the second parameter is a negative value, it is the number starting from the end. The first parameter at the end is-1, followed by-2 to the left,-3...

If the third parameter is omitted, it starts from the second parameter to the end of the string.

Substr ($ big, 0, 5) = "zhouxiang" to perform this operation will change the original string.

Only the part of the string can be operated.

You can also take the part to be assigned as the fourth parameter to achieve the same effect.

Sprintf and printf have the same parameters, but sprintf returns the string to be requested instead of outputting it

 

Advanced sorting

Similar to the compareable interface in Java

You only need to specify the order relationship between the two elements to be sorted.

$ A <$ B-1

$ A> $ B 1

$ A = $ B, $ A and $ B do not distinguish size 0

Usage

Sort subroutine data

Note: Generally, child routines are named _.

Shorthand

Compare the number spacecraft operator <=> and return-1, 0, 1.

String CMP