Shell if expressions

1. Shell expression

A = 3; B = 2; C = 4

If (A> B) & (A <C ))

Or

If [[$ A> $ B] & [[$ A <$ C]

Or

If [$ A-GT $ B-A $ A-lt $ C]

2.-O = or,-A = And, but I have always used | or &&

3. Other explanations

-Ne comparison number (numberic );! = Comparison character (string), but the latter can also be used to compare numbers, but it is not a standard usage.

-Lt is Equivalent <, but <It can only be used in Shell numeric operators () or intercept operators [].,-Lt,-EQ,-GT,-Ge,-Le,These are test, which is the conditional operator used by the [] built-in command,Used to compare numbers; = ,! = Use to compare characters; = This is used in [[]. It can be used to compare regular expressions, but it can also be used in [], but it is not quite orthodox.

In addition, there are many other comparable test expressions [], such as comparison of files and directories.

Original article:

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