if 條件測試語句

then

action

[elif 條件

action

else

action

]

fi

[chengmo@centos5 ~]$ a=5;if [[ a -gt 4 ]] ;then echo 'ok';fi;                   
ok

#!/bin/sh

scores=40;
if [[ $scores -gt 90 ]]; then
    echo "very good!";
elif [[ $scores -gt 80 ]]; then
    echo "good!";
elif [[ $scores -gt 60 ]]; then
    echo "pass!";
else
    echo "no pass!";
fi;

1.for … in 語句

for 變量 in seq字符串

do

action

done

#!/bin/sh

for i in $(seq 10); do
    echo $i;
done;

for((賦值；條件；運算語句))

do

action

done;

#!/bin/sh

for((i=1;i<=10;i++));do
    echo $i;
done;

while 條件語句

do

action

done;

#!/bin/sh
i=10;
while [[ $i -gt 5 ]];do
    echo $i;
    ((i--));
done;

sh testwhile1.sh
10
9
8
7
6

#!/bin/sh

while read line;do
    echo $line;
done < /etc/hosts;

sh testwhile2.sh

# Do not remove the following line, or various programs
# that require network functionality will fail.
127.0.0.1 centos5 localhost.localdomain localhost

until 條件

do

action

done

#!/bin/sh

a=10;

until [[ $a -lt 0 ]];do

echo $a;

((a―));

done;

10
9
8
7
6
5
4
3
2
1
0

case $arg in 
    pattern | sample) # arg in pattern or sample 

    pattern1) # arg in pattern1 

    *) #default 

esac

#!/bin/sh

case $1 in
start | begin)
    echo "start something" 

stop | end)
    echo "stop something" 

*)
    echo "Ignorant" 

esac

testcase.sh start
start something

select 變量name  in seq變量

do

    action

done

#!/bin/sh

select ch in "begin" "end" "exit"
do
case $ch in
"begin")
    echo "start something" 

"end")
    echo "stop something" 

"exit")
    echo "exit" 
    break;

*)
    echo "Ignorant" 

esac
done;