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Assigning values to variables

Defining an integer class using Declare-i

[[email protected] scripts]# Aa=5+6[[email protected] scripts]# echo $aa 5+6[[email protected] scripts]# declare-i Aa[[ema Il protected] scripts]# aa=5+6[[email protected] scripts]# echo $AA 11

With let, you don't need to define an integral type

[[email protected] scripts]# let Bb=1+8[[email protected] scripts]# echo $bb 9[[email protected] scripts]# cc=$ ((5+8)) [[Em AIL protected] scripts]# echo $CC 13

echo $? return value

Test compare two worth of size

-eq-lt-le-gt-ge

Aa=3 bb=4

Test $aa-eq $BB

echo $?

Test $aa-lt $BB

echo $?

Judgment 1 | | Judgment 2

[-F/ETC/PASSWD] Determine if the file exists

echo $?

0

[-R/ETC/PASSWD]

echo $?

0

[Email protected] scripts]# aa=3 bb=4[[email protected] scripts]# [$aa-lt $BB] && echo okok[[email protected] scripts]# [$aa-gt $bb] && echo OK [[email protected] scripts]# [$aa-gt $BB] | | echo OK OK

Judging the Code

[[email protected] scripts]# vim if.sh#!/bin/bashgrep-q ^$1/etc/passwdif ["$?"-eq 0]; Then echo "$ is exist" else echo "exist" fi

If...then

[Email protected] scripts]# vim age.sh#!/bin/bashread-p "Please input your Age:" Ageif ["$age"-le 0] | | ["$age"-ge 100]; then echo "Please input correct age" Read Ageelif ["$age"-GT 0] && ["$age"-lt 20]; Then echo "Junior" Elif ["$age"-ge] && ["$age"-lt 50]; Then echo "You is adult" else echo "You is old" fi

While loop

[Email protected] scripts]# vim sum.sh#!/bin/bashsum=0while [$sum-lt]do let Sum+=1 echo $sumdone

#!/bin/bashread-p "Please input your name:" Namewhile ["$name"! = Tom] do echo "Please input correct name" Read namedone~

[[email protected] scripts]# vim case.sh#!/bin/bashxx=0until [  "$xx"  -gt  24 ]do        case  "$xx"  in                 [0-9]|1[01])                           echo  "Good morning"                          ;;                 12)                           echo  "It ' S lunch time"                          ;;                 1[3-7])                           echo  "Good afternoon"                          ;;                 *)                           echo  "Good evening"         esac          let xx+=1done

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