Shell if else囂鞘

<貧匯准和匯准>

if 囂鞘宥狛購狼塰麻憲登僅燕器塀議寔邪栖畳協峇佩陳倖蛍屶。Shell 嗤眉嶽 if ... else 囂鞘?

if ... fi 囂鞘?
if ... else ... fi 囂鞘?
if ... elif ... else ... fi 囂鞘。

1) if ... else 囂鞘

if ... else 囂鞘議囂隈?

if [ expression ]
then
 Statement(s) to be executed if expression is true
fi

泌惚 expression 卦指 true?then 朔円議囂鞘繍氏瓜峇佩?泌惚卦指 false?音氏峇佩販採囂鞘。

恷朔駅倬參 fi 栖潤硫液栽 if?fi 祥頁 if 宜狛栖憧亟?朔中匆氏囑需。

廣吭?expression 才圭凄催([ ])岻寂駅倬嗤腎鯉?倦夸氏嗤囂隈危列。

訟倖箭徨?

#!/bin/sh
a=10
b=20
if [ $a == $b ]
then
 echo "a is equal to b"
fi
if [ $a != $b ]
then
 echo "a is not equal to b"
fi

塰佩潤惚?

a is not equal to b

2) if ... else ... fi 囂鞘

if ... else ... fi 囂鞘議囂隈?

if [ expression ]
then
 Statement(s) to be executed if expression is true
else
 Statement(s) to be executed if expression is not true
fi

泌惚 expression 卦指 true?椎担 then 朔円議囂鞘繍氏瓜峇佩?倦夸?峇佩 else 朔円議囂鞘。

訟倖箭徨?

#!/bin/sh
a=10
b=20
if [ $a == $b ]
then
 echo "a is equal to b"
else
 echo "a is not equal to b"
fi

峇佩潤惚?

a is not equal to b

3) if ... elif ... fi 囂鞘

if ... elif ... fi 囂鞘辛參斤謹倖訳周序佩登僅?囂隈葎?

if [ expression 1 ]
then
 Statement(s) to be executed if expression 1 is true
elif [ expression 2 ]
then
 Statement(s) to be executed if expression 2 is true
elif [ expression 3 ]
then
 Statement(s) to be executed if expression 3 is true
else
 Statement(s) to be executed if no expression is true
fi

陳匯倖 expression 議峙葎 true?祥峇佩陳倖 expression 朔中議囂鞘?泌惚脅葎 false?椎担音峇佩販採囂鞘。

訟倖箭徨?

#!/bin/sh
a=10
b=20
if [ $a == $b ]
then
 echo "a is equal to b"
elif [ $a -gt $b ]
then
 echo "a is greater than b"
elif [ $a -lt $b ]
then
 echo "a is less than b"
else
 echo "None of the condition met"
fi

塰佩潤惚?

a is less than b

if ... else 囂鞘匆辛參亟撹匯佩?參凋綜議圭塀栖塰佩?崧宸劔?

if test $[2*3] -eq $[1+5]; then echo 'The two numbers are equal!'; fi;

if ... else 囂鞘匆将械嚥 test 凋綜潤栽聞喘?泌和侭幣?

num1=$[2*3]
num2=$[1+5]
if test $[num1] -eq $[num2]
then
 echo 'The two numbers are equal!'
else
 echo 'The two numbers are not equal!'
fi

補竃?

The two numbers are equal!

test 凋綜喘噐殊臥蝶倖訳周頁倦撹羨?嚥圭凄催([ ])窃貌。

<貧匯准和匯准>

Shell if else囂鞘

1) if ... else 囂鞘

2) if ... else ... fi 囂鞘

3) if ... elif ... fi 囂鞘

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