while [ condition ]  <==中括号内的状态就是判断式
do            <==do 是回圈的开始！程序段落
done          <==done 是回圈的结束

until [ condition ]
do程序段落
done

[root@www scripts]# vi sh13.sh
#!/bin/bash
# Program:
#   Repeat question until user input correct answer.
# History:
# 2005/08/29    VBird   First release
PATH=/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin:~/bin
export PATHwhile [ "$yn" != "yes" -a "$yn" != "YES" ]
doread -p "Please input yes/YES to stop this program: " yn
done
echo "OK! you input the correct answer."

[root@www scripts]# vi sh13-2.sh
#!/bin/bash
# Program:
#   Repeat question until user input correct answer.
# History:
# 2005/08/29    VBird   First release
PATH=/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin:~/bin
export PATHuntil [ "$yn" == "yes" -o "$yn" == "YES" ]
doread -p "Please input yes/YES to stop this program: " yn
done
echo "OK! you input the correct answer."

[root@www scripts]# vi sh14.sh
#!/bin/bash
# Program:
#   Use loop to calculate "1+2+3+...+100" result.
# History:
# 2005/08/29    VBird   First release
PATH=/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin:~/bin
export PATHs=0  # 这是加总的数值变量
i=0  # 这是累计的数值，亦即是 1, 2, 3....
while [ "$i" != "100" ]
doi=$(($i+1))   # 每次 i 都会添加 1 s=$(($s+$i))  # 每次都会加总一次！
done
echo "The result of '1+2+3+...+100' is ==> $s"

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

[root@www scripts]# vi sh15.sh
#!/bin/bash
# Program:
#   Using for .... loop to print 3 animals
# History:
# 2005/08/29    VBird   First release
PATH=/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin:~/bin
export PATHfor animal in dog cat elephant
doecho "There are ${animal}s.... "
done

[root@www scripts]# vi sh16.sh
#!/bin/bash
# Program
#       Use id, finger command to check system account's information.
# History
# 2009/02/18    VBird   first release
PATH=/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin:~/bin
export PATH
users=$(cut -d ':' -f1 /etc/passwd)  # 撷取帐号名称
for username in $users               # 开始回圈进行！
doid $usernamefinger $username
done

[root@www scripts]# vi sh17.sh
#!/bin/bash
# Program
#       Use ping command to check the network's PC state.
# History
# 2009/02/18    VBird   first release
PATH=/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin:~/bin
export PATH
network="192.168.1"              # 先定义一个网域的前面部分！
for sitenu in $(seq 1 100)       # seq 为 sequence(连续) 的缩写之意
do# 底下的程序在取得 ping 的回传值是正确的还是失败的！ping -c 1 -w 1 ${network}.${sitenu} &> /dev/null && result=0 || result=1# 开始显示结果是正确的启动 (UP) 还是错误的没有连通 (DOWN)if [ "$result" == 0 ]; thenecho "Server ${network}.${sitenu} is UP."elseecho "Server ${network}.${sitenu} is DOWN."fi
done

[root@www scripts]# vi sh18.sh
#!/bin/bash
# Program:
#   User input dir name, I find the permission of files.
# History:
# 2005/08/29    VBird   First release
PATH=/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin:~/bin
export PATH# 1. 先看看这个目录是否存在啊？
read -p "Please input a directory: " dir
if [ "$dir" == "" -o ! -d "$dir" ]; thenecho "The $dir is NOT exist in your system."exit 1
fi# 2. 开始测试文件罗～
filelist=$(ls $dir)        # 列出所有在该目录下的文件名称
for filename in $filelist
doperm=""test -r "$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

for (( 初始值; 限制值; 运行步阶 ))
do程序段
done

[root@www scripts]# vi sh19.sh
#!/bin/bash
# Program:
#   Try do calculate 1+2+....+${your_input}
# History:
# 2005/08/29    VBird   First release
PATH=/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin:~/bin
export PATHread -p "Please input a number, I will count for 1+2+...+your_input: " nus=0
for (( i=1; i<=$nu; i=i+1 ))
dos=$(($s+$i))
done
echo "The result of '1+2+3+...+$nu' is ==> $s"