Shell instance (i)

Shell instance (i)

• Example one:

equals-eq (equal)

Unequal-ne (not equal)

Greater than-GT (greater than)

Smaller than-lt (less than)

Greater than or equal to-ge (greater than or equal)

Less than or equal to-le (lesser than or equal)

Examples are as follows:

#！ /bin/bash

d= ' Date '

Echo $d

A=1

If [$a-lt 3] ==if (($a < 3))

Then

echo "This is OK"

Fi

The results are as follows:

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• Example two:

Determine whether the number entered is even or odd

#!/bin/bash

Read-p "Please enter a number:" N

n1=$[$n%2]

If [$n 1-eq 0]

Then

echo "Number entered is even"

Else

echo "Number entered is odd"

Fi

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• example Three: for the above example extension, if the input is not a pure number, what should be done?

#!/bin/bash

Read-p "Please enter a number:" N

N2= ' echo $n |grep-c ' [^0-9] '

If [$n 2-eq 1]

Then

echo "You are not entering a pure number, please re-enter"

Exit 1

Fi

n1=$[$n%2]

If [$n 1-eq 0]

Then

echo "The number you entered is even"

Else

echo "The number you entered is odd"

Fi

Note: When you exit 0, in the call environment echo $? Returns 0, which means that the calling environment thinks your program executes correctly; When you exit 1, it's usually a mistake to define the 1, or it can be another number, many system programs this error number is the meaning of the Convention. but not 0 means that the program is running in error. The calling environment allows you to determine whether the program is running OK based on the return value.

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• Example four:

#if [-E 1.sh];then echo "1.sh exist"; fi = = #[-e 1.sh] && echo "1.sh exist"

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• Example five:

#!/bin/bash

d= ' Date +%f '

exec >/tmp/$d. log 2> &1 "&1 stands for tmp/$d. Log"

echo "begin at ' Date '"

Ls/tmp/sdade

cd/shdwduw/

echo "End at ' Date '"

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This article is from the "Hand of the Paladin Control" blog, please make sure to keep this source http://wutengfei.blog.51cto.com/10942117/1910829

Shell instance (i)