while循环：条件满足，则循环；失败，则退出
如何退出？
必须有时刻，条件测试不成功
? :条件控制变量
while 条件测试：do
循环体
done
until循环；条件不满足，则循环；否则，退出
until 测试条件；do
循环体
done
bash编程之组合测试条件
逻辑与：多个条件同时满足
[ CONDITION1 ] && [ CONDITION2 ]
[ CONDITION1 -a CONDITION2 ]
[[ CONDITION1 && CONDITION2 ]]
注意：前两个使用单双中括号都可，但&&不允许用于单个中括号中，所有第三者只能用于双中括号中
逻辑或：多个条件满足一个
[ CONDITION1 ] || [ CONDITION2 ]
[ CONDITION1 -o CONDITION2 ]
[[ CONDITION1 || CONDITION2 ]]
注意 || 不允许出现在单中括号中
得摩根定律
!(条件1或者 条件2) = !条件1 并且!条件2
!（条件1且条件2）=！条件1 或者 !条件2
练习:
1.：通过键盘提示用户输入字符，将用户输入的小写字母转换为大写，转换一次之后，在此提醒，再输入再转换，直到输入quit退出；
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#！ /bin/bash
#
read
-p -t 5
"Enter a Word: "
word
while
[[
"$word"
!=
"quit"
]];
do
echo
$word |
tr
'a-z'
'A-Z'
read
-p -t 5
"Enter a Word again: "
word
done
|
2.写一个脚本，实现如下功能；
1、显示如下菜单：
CPU) show cpu info;
men) show memory info;
disk) show disk info;
quit) quit
Enter your option:
2、根据用户的选择输出相应信息，每次执行后，不退出，而由用户咋此指定新的选项
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#! /bin/bash
#
cat
<<EOF
cpu) print cpu infomation
men) print memory infomation
disk) print disk infomation
quit) Quit
EOF
read
-p
"Enter your option: "
option
option=`
echo
$option |
tr
'a-z'
'A-Z'
`
while
[[
"$option"
!=
"QUIT"
]];
do
if
[[
"$option"
==
"CPU"
]];
then
cat
/proc/cpuinfo
elif
[[
"$option"
==
"MEM"
]];
then
free
-m
elif
[[
"$option"
==
"DISK"
]];
then
df
-Th
else
echo
"Wrong Option..."
fi
read
-p
"Enter your option: "
option
option=`
echo
$option |
tr
'a-z'
'A-Z'
`
done
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3.提示用户输入一个用户名，显示用户名UID和SHELl信息，否则，则显示无此用户，显示完成后，提示用户再次输入，如果quit则退出；
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#! /bin/bash
#
cat
<<EOF
Username)Enter your Username..
quit)quit..
EOF
read
-p
"Enter Your userName: "
userName
userName=`
echo
$userName |
tr
'A-Z'
'a-z'
`
while
[[
"$userName"
!=
"QUIT"
]];
do
sysUser=`
cat
/etc/passwd
|
grep
^$userName |
cut
-d: -f1 |
tr
'A-Z'
'a-z'
`
if
[[
"$userName"
==
"$sysUser"
]];
then
echo
"This $userName `cat /etc/passwd | grep -i ^$userName | cut -d: -f3,7`"
else
echo
"No Such $userName.."
fi
read
-p
"Enter Your userName: "
userName
userName=`
echo
$userName |
tr
'A-Z'
'a-z'
`
done
#! /bin/bash
#
read
-t 2 -p
"Enter a user name: "
userName
userName=`
echo
$userName |
tr
'A-Z'
'a-z'
`
UID=`
grep
"^$userName\>"
/etc/passwd
|
cut
-d: -f3`
SH=`
grep
"^$userName\>"
/etc/passwd
|
cut
-d: -f7`
while
[[
"$userName"
!=
"quit"
]];
do
if
[ -z
"$userName"
];
then
echo
"Username null...."
elif
id
$userName &>
/dev/null
;
then
echo
"$userName uid: $UID"
echo
"$userName Shell: $SH"
else
echo
"No such user...."
fi
read
-t 2 -p
"Enter a user name again(quit to exit) "
userName
done
|
4.求100以内所有正整数的和；
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#! /bin/bash
#
declare
-i
sum
=0
declare
-i i=1
while
[ $i -
le
100 ];
do
let
sum
+=$i
let
i++
done
echo
$
sum
#! /bin/bash
#
declare
-i
sum
=0
declare
-i i=1
until
[ $i -gt 100 ];
do
let
sum
+=$i
let
i++
done
echo
$
sum
|
5.求100以内所有偶数之和；
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#! /bin/bash
#
declare
-i evensum=0
declare
-i i=1
while
[ $i -
le
100 ];
do
if
[ $[$i%2] -
eq
0 ];
then
let
evensum+=$i
fi
let
i++
done
echo
$evensum
#! /bin/bash
#
declare
-i
sum
=0
declare
-i i=0
while
[[ $i -
le
100 ]];
do
let
sum
+=$i
let
i+=2
done
echo
$
sum
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6.用until求100以内整数之和；
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#! /bin/bash
#
declare
-i
sum
=0
declare
-i i=1
until
[ $i -gt 100 ];
do
let
sum
+=$i
let
i++
done
echo
$
sum
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7.提供一个用户名，判断用户是否登陆当前系统；
1.如果没有登陆，则停止5秒之后再次判断，直到用户登录系统，显示用户登录，而后退出
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#! /bin/bash
#
read
-t 5 -p
"Enter Your userName: "
userName
userName=`
echo
$userName |
tr
'A-Z'
'a-z'
`
who
|
grep
"$userName"
&>
/dev/null
retVal=$?
while
[ $retVal -
ne
0 ];
do
sleep
5
read
-t 5 -p
"Enter Your userName: "
userName
userName=`
echo
$userName |
tr
'A-Z'
'a-z'
`
done
echo
"Welcome $userName login System..."
#! /bin/bash
#
read
-t 5 -p
"Enter Your userName: "
userName
while
!
id
$userName &>
/dev/null
;
do
read
-t 5 -p
"Enter Your userName: "
userName
done
who
|
grep
"^$userName"
&>
/dev/null
retVal=$?
while
[ $retVal -
ne
0 ];
do
sleep
5
who
|
grep
"$userName"
&>
/dev/null
retVal=$?
done
echo
"Welcome $userName login System..."
#! /bin/bash
#
read
-t 5 -p
"Enter Your userName: "
userName
while
!
id
$userName &>
/dev/null
;
do
read
-t 5 -p
"Enter Your userName again: "
userName
done
while
!
who
|
grep
"^$userName"
&>
/dev/null
;
do
sleep
5
done
echo
"Welcome $userName login System..."
#! /bin/bash
#
read
-t 5 -p
"Enter Your userName: "
userName
until
[ -n
"$userName"
] &&
id
$userName &>
/dev/null
;
do
read
-t 5 -p
"Enter Your userName again: "
userName
done
until
who
|
grep
"^$userName"
&>
/dev/null
;
do
sleep
5
done
echo
"Welcome $userName login System..."
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8.取出当前系统上，默认shell为bash的用户；
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#! /bin/bash
#
while
read
line;
do
[[ `
echo
$line |
cut
-d: -f7` ==
"/bin/bash"
]] &&
echo
$line |
cut
-d: -f1
done
<
/etc/passwd
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9.显示其ID号为偶数的用户；
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#! /bin/bash
#
while
read
line;
do
userID=`
echo
$line |
cut
-d: -f3`
if
[ $[$userID%2] -
eq
0 ];
then
echo
-n
"$userID: "
echo
$line |
cut
-d: -f1
fi
done
<
/etc/passwd
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10.显示/etc/rc.d/rc.sysinit文件中，其总字符个数大于30的行；
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#! /bin/bash
#
while
read
line;
do
charCounts=`
echo
$line |
wc
-c`
if
[ $charCounts -gt 30 ];
then
echo
-n
"$charCounts: "
echo
$line
fi
done
<
/etc/rc
.d
/rc
.sysinit
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11.显示用户其UID和GID均为偶数的用户；
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#! /bin/bash
#
while
read
line;
do
userID=`
echo
$line |
cut
-d: -f3`
groupID`
echo
$line |
cut
-d: -f4`
if
[ $[$userID%2] -
eq
0 -a $[$groupID%2] -
eq
0 ];
then
echo
-n
"$userID,$groupID: "
echo
$line |
cut
-d: -f1
fi
done
<
/etc/passwd
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12.显示/etc/rc.d/rc.sysinit文件中，其总字符个数大于30且以非#开头的行；
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#! /bin/bash
#
while
read
line;
do
charCounts=`
echo
$line |
wc
-c`
if
[ $charCounts -gt 30 ] && [[
"$line"
=~ ^[^
#] ]]; then
echo
-n
"$charCounts: "
echo
$line
fi
done
<
/etc/rc
.d
/rc
.sysinit
|
13.写一个脚本，完成如下任务；
1.提示用户输入一个磁盘设备文件路径不存在或不是一个块设备，则提示用户重新输入，知道输入正确为止，或者输入quit以9为退出码结束脚本
2.提示用户"下面的操作会清空磁盘的数据，并提问是否继续"
如果用户给出字符y或yes，则继续，否则，则提供以8为退出码结束脚本
3.将用户指定的磁盘上的分区清空，而后创建两个分区，大小分别为100M和512M
4.格式化这两个分区
5.将第一个分区挂载至/mnt/boot目录，第二个分区挂载至/mnt/sysroot目录