(go) Shell script file test operators and integer comparators

Shell script file test operators and integer comparators

Original: http://www.cnblogs.com/Steward-Xu/p/6722592.html

First, the file test operator:

In writing the test expression is, you can use the file to test the operator.

　　

　　More parameters can help test or man bash

Second, the string test operator:

　　The role of the string test operator is to compare whether two strings are the same, whether the character length is 0, whether the string is null (NOTE: Bash distinguishes between length strings and empty strings)

"=" compares two strings in the same way as "= =", such as if ["$a" = "$b"], where a variable of $ A is best enclosed in "" because if there are spaces in the middle there will be an error. A better approach is if ["${a}" = "${b}"].

'! = ' compares two strings for the same and is true for different characters.

The writing expression is available with the following test action symbols:

　　

Three, integer two-dollar comparison operator:

It contains:-eq,-ne,-gt,-ge,-lt, and-le used in [] the comparison character

= =,! =, >, >=, <, <= used in () and [[]]

　　

Four: numerical calculation of variables: Includes: "^", "! =", and assignment operations. 　　

　　

　　Practical Examples:

Examples of multi-condition string tests:

　　

 1 [[email protected]/]# [-Z "$file 1"] && echo ture | | echo False 2 ture 3 [[email protected]/]# [-N "$file 1"] && echo ture | | Echo False 4 False 5 [[[Email protected]/]# [-z] $file 1 "-a-z" $file 2 "] && echo ture | | echo false 6 ture 7 [[email protected]/]# [-N "$file 1"-a-n "$file 2"] && echo ture | | Echo false 8 False 9 [[email protected]/]# [-N "$file 1"-o-n "$file 2"] && echo ture | | echo False False11 [[email protected]/]# [-N "$file 1"-o-z "$file 2"] && echo ture | | echo False Ture13 [[[Email protected]/]# [["$file 1" = "$file 2"]] && echo true | | echo False True15 [[email protected]/]# [["$file 1"! = "$file 2"]] && echo true | | echo False16 false17 [[email protected]/]# [[-N $file 1 &&-n $file 2]] && echo true | | echo False18 false19 [[[Email protected]/]# [[-N $file 1 | |-n $file 2]] && echo true | | echo False False21 [[email protected]/]# [[-N $file 1 | |-Z $file 2]] && echo true | | Echo False22 True

　　　　Examples of integer tests:

　　

　　

1 [[Email protected]/]# a1=12 2 [[email protected]/]# a2=13 3 [[email protected]/]# [$a 1 = $a 2] && echo True || Echo False 4 false 5 [[email protected]/]# [$a 1! = $a 2] && echo true | | Echo False 6 True 7 [[email protected]/]# [$a 1-le $a 2] && echo true | | echo False   8 true 9 [[email protected]/]# [$a 1-ge $a 2] && echo true | | echo false FALSE11 [email prote CTED]/]# [$a 1-gt $a 2] && echo true | | echo False False13 [[email protected]/]# [$a 1-lt $a 2] && echo true | | echo False TRUE15 [[email protected]/]# [$a 1-eq $a 2] && echo true | | echo False  false17 [[email protected]/]# echo $a 1 $a 218 12 13

(go) Shell script file test operators and integer comparators