Use of the Shell Foundation--test command

Test: For file type checking and variable comparison

A. Use:

1. Judging expressions

　

2. Judging the string

3. Judging integers

4. Judging documents

Test examples:

(1). Test

[Email protected] ~_~ day5]# cat test.sh

#!/bin/bash

A=$1

B=$2

if test $a-eq $b

Then

echo "A=b"

Else

echo "A!=b"

Fi

[[email protected] ~_~ day5]# sh test.sh 1 1

A=b

[[email protected] ~_~ day5]# sh test.sh 1 2

A!=b

---------------------------------------------

(2). []

[Email protected] ~_~ day5]# cat test.sh

#!/bin/bash

A=$1

B=$2

[$a = $b] && echo "A=b" | | echo "A!=b"

[[email protected] ~_~ day5]# sh test.sh 1 2

A!=b

[[email protected] ~_~ day5]# sh test.sh 1 1

A=b

-------------------------------------------------

(3). judgment file

[Email protected] ~_~ day5]# cat test2.sh

#!/bin/bash

[-F "$"]&& echo "$ is a file" | | echo "$ is not a file"

[Email protected] ~_~ day5]# sh test2.sh

Test2.sh is a file

Two. test,[], [[]] usage comparison

[] equivalent to test, both the shell gets the internal command, and [[]] is the shell to get the keyword, bash the expression in double brackets as a separate element, and return an exit status code, it is recommended to use [[]] as a conditional judgment statement, not easy to appear logic error. Also, [[]] supports pattern matching and regular expressions

(1). Syntax comparison

[[]]: if [[$a! = 1 && $a! = 2]]

[]: If [$a-ne 1] && [$a! = 2] or if [$a-ne 1-a $a! = 2]

(2). [[]] Support pattern matching

[Email protected] ~_~ day5]# cat test4.sh

#!/bin/bash

[["ABCD" = = A*d]]&& echo True | | Echo flase

["abcd" = = A*d]&& echo True | | Echo flase

[Email protected] ~_~ day5]# sh test4.sh

True

Flase

(3). [[]] supports regular expressions

[Email protected] ~_~ day5]# cat test5.sh

[["Hello" =~ ^h]]&& echo Ture | | Echo False

[Email protected] ~_~ day5]# sh test5.sh

Ture

Use of the Shell Foundation--test command