Shell Programming---Character testing and for loops

A. Character test

= =: Test for equality, equality is true, not equal to False

! =: Test Whether it is unequal, not equal to true, etc as false

>

<

-N String: Tests whether the specified string is empty, empty is true, or false

-Z String: Tests whether the specified string is not empty, is not empty, and the null is False

[$username = = $useername 1] There must be spaces at both ends of the equals sign

1.bc

echo "SCALE=2;111/22;" | BC calculates two number of reserved two decimal places

Exercise: Write a script

Pass a parameter (single-character on line) to the script, such as Q, Q, quit, or quit, to exit the script, otherwise, the user's parameters are displayed;

#!/bin/bash

#

if [$ = ' Q '];then

echo "Quiting ..."

Exit 1

elif [$ = ' Q '];then

echo "Quiting ..."

Exit 2

elif [$ = ' Quit '];then

echo "Quiting ..."

Exit 3

elif [$ = ' Quit '];then

echo "Quiting ..."

Exit 4

Else

echo $

Fi

2.for Cycle

For I in {1...10}; Do

Addition operation

Done

Write a script:

Calculates the sum of all odd and all and all even numbers within 100, respectively, showing the

#/bin/bash

#

Declare-i oddsum=0

Declare-i evensum=0

Declare-i s

For I in {1..100};d o

Let s=$[$I%2]

If [$s-eq 0];then

Let oddsum=$[$oddsum + $I]

elif [$s-eq 1];then

Let evensum=$[$evensum + $I]

Fi

Done

Echo ${oddsum}---${evensum}

Combination test conditions

-A: With relation

-O: or relationship

!: Non-relational

If [$#-gt 1-a $#-le 3]

If [$#-gt 1] && [$#-le 3]

This article is from "Luo Chen's blog" blog, please be sure to keep this source http://luochen2015.blog.51cto.com/9772274/1637233

Shell Programming---Character testing and for loops