(A) the while loop
The while loop is used by default to segment the carriage return, so the while loop for processing the text. After the required data on the use of the text line by line processing while, in fact, simply not suitable for loop processing text Ha!
while loop will not skip blank lines in the face, he would empty his as a variable. Therefore, while using the line when the need for variable length determination.
1. while the grammatical structure
Example one: while loop initialization batch creation of users and passwords
Example Two: while test whether a remote host is through
(Ii) an until loop
1. until grammatical structure:
Example one: until test whether through the remote host
Example 2: 1-100 accumulated value calculated by cyclic
let sum = $ sum + $ i and let sum + = $ i are equivalent
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