25 shell编程 循环语句 for循环 while循环 until循环 案例；批量解压文件_使用until语句实现输出当前目录下的所有文件

while do done

当 condition 条件成立时，就进行循环，直到 condition 的条件不成立才停止

while [ condition ]  <==中括号内的状态就是判断式
do            <==do 是循环的开始！
	程序段落
done          <==done 是循环的结束
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[userwin@MiWiFi-R3L-srv sh]$ vim while1.sh 

#!/bin/bash
while [ "$yn" != "yes" -a "$yn" != "YES" ]
do
        read -p "Please input yes/YES to stop this program: " yn
done
echo "OK! you input the correct answer."

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[userwin@MiWiFi-R3L-srv sh]$ sh while1.sh 
Please input yes/YES to stop this program: a
Please input yes/YES to stop this program: b
Please input yes/YES to stop this program: yes
OK! you input the correct answer.
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[userwin@MiWiFi-R3L-srv sh]$ vim while2.sh 

#!/bin/bash

# 1加到100 求和
i=1
s=0
while [ $i -le 100 ]
do
        s=$(( $s+$i ))
        i=$(( $i+1 ))
done
echo "the sum is $s"

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[userwin@MiWiFi-R3L-srv sh]$ sh while2.sh 
the sum is 5050

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until do done

当 condition 条件成立时，就终止循环， 否则就持续进行循环的程序段。

until [ condition ]
do
	程序段落
done
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[userwin@MiWiFi-R3L-srv sh]$ vim until1.sh 

#!/bin/bash
until [ "$yn" == "yes" -o "$yn" == "YES" ]
do
        read -p "Please input yes/YES to stop this program: " yn
done
echo "OK! you input the correct answer."
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[userwin@MiWiFi-R3L-srv sh]$ sh until1.sh 
Please input yes/YES to stop this program: a
Please input yes/YES to stop this program: b
Please input yes/YES to stop this program: YES
OK! you input the correct answer.

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[userwin@MiWiFi-R3L-srv sh]$ vim until2.sh 

#!/bin/bash

# 1加到100 求和
i=1
s=0
until [ $i -gt 100 ]
do
        s=$(( $s+$i ))
        i=$(( $i+1 ))
done
echo "the sum is $s"

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[userwin@MiWiFi-R3L-srv sh]$ sh until2.sh 
the sum is 5050

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for…do…done

for var in con1 con2 con3 ...
do
	程序段
done
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场景一

[userwin@MiWiFi-R3L-srv sh]$ vim for1.sh 

#!/bin/bash
for animal in dog cat elephant
do
        echo "There are ${animal}s.... "
done

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[userwin@MiWiFi-R3L-srv sh]$ sh for1.sh 
There are dogs.... 
There are cats.... 
There are elephants.... 
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场景二

[userwin@MiWiFi-R3L-srv sh]$ vim for2.sh 

#!/bin/bash

users=$(cut -d ':' -f1 /etc/passwd)  # 撷取帐号名称
for username in $users               # 开始回圈进行！
do
        echo "username : ${username}"
done

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[userwin@MiWiFi-R3L-srv sh]$ sh for2.sh 
username : root
username : bin
username : daemon
username : adm
username : lp
username : sync
username : shutdown

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场景三

[userwin@MiWiFi-R3L-srv sh]$ vim for3.sh 

#!/bin/bash
for index in $(seq 1 100)       # seq 为 sequence(连续) 的缩写之意
do
        echo "index : $index"
done
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[userwin@MiWiFi-R3L-srv sh]$ sh for3.sh 
index : 1
index : 2
index : 3
index : 4
index : 5
index : 6
index : 7
index : 8
index : 9
index : 10
index : 11
index : 12
index : 13
index : 14
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index : 88
index : 89
index : 90
index : 91
index : 92
index : 93
index : 94
index : 95
index : 96
index : 97
index : 98
index : 99
index : 100
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场景四

# 查看目录是否存在
read -p "Please input a directory: " dir
if [ "$dir" == "" -o ! -d "$dir" ]; then
	echo "The $dir is NOT exist in your system."
	exit 1
fi

# 存在； 则循环目录下的文件
filelist=$(ls $dir)        # 列出所有在该目录下的文件名称
for filename in $filelist
do
	perm=""
	test -r "$dir/$filename" && perm="$perm readable"
	test -w "$dir/$filename" && perm="$perm writable"
	test -x "$dir/$filename" && perm="$perm executable"
	echo "The file $dir/$filename's permission is $perm "
done
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for…do…done 的数值处理

for (( 初始值; 限制值; 运行步阶 ))
do
	程序段
done
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[userwin@MiWiFi-R3L-srv sh]$ vim for4.sh 

#!/bin/bash
read -p "Please input a number, I will count for 1+2+...+your_input: " nu

s=0
for (( i=1; i<=$nu; i=i+1 ))
do
        s=$(($s+$i))
done
echo "The result of '1+2+3+...+$nu' is ==> $s"
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[userwin@MiWiFi-R3L-srv sh]$ sh for4.sh 
Please input a number, I will count for 1+2+...+your_input: 100
The result of '1+2+3+...+100' is ==> 5050

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# 批量解压文件
[userwin@MiWiFi-R3L-srv sh]$ vim for4.sh 

#!/bin/bash

cd $HOME/targzs
ls *.tar.gz>ls.log
for tarFlie in $(cat ls.log)
do
	tar -zxf $tarFile &>/dev/null
done
rm -rf $HOME/targzs/ls.log
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