while循環：條件滿足，則循環；失敗，則退出
如何退出？
必須有時刻，條件測試不成功
? :條件控制變量
while 條件測試：do
循環體
done
until循環；條件不滿足，則循環；否則，退出
until 測試條件；do
循環體
done
bash編程之組合測試條件
邏輯與：多個條件同時滿足
[ CONDITION1 ] && [ CONDITION2 ]
[ CONDITION1 -a CONDITION2 ]
[[ CONDITION1 && CONDITION2 ]]
注意：前兩個使用單雙中括號都可，但&&不允許用於單個中括號中，所有第三者只能用於雙中括號中
邏輯或：多個條件滿足一個
[ CONDITION1 ] || [ CONDITION2 ]
[ CONDITION1 -o CONDITION2 ]
[[ CONDITION1 || CONDITION2 ]]
注意 || 不允許出現在單中括號中
得摩根定律
!(條件1或者 條件2) = !條件1 並且!條件2
!（條件1且條件2）=！條件1 或者 !條件2
練習:
1.：通過鍵盤提示用戶輸入字符，將用戶輸入的小寫字母轉換為大寫，轉換一次之后，在此提醒，再輸入再轉換，直到輸入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.寫一個腳本，實現如下功能；
1、顯示如下菜單：
CPU) show cpu info;
men) show memory info;
disk) show disk info;
quit) quit
Enter your option:
2、根據用戶的選擇輸出相應信息，每次執行后，不退出，而由用戶咋此指定新的選項
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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
|
3.提示用戶輸入一個用戶名，顯示用戶名UID和SHELl信息，否則，則顯示無此用戶，顯示完成后，提示用戶再次輸入，如果quit則退出；
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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以內所有正整數的和；
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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以內所有偶數之和；
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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以內整數之和；
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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.提供一個用戶名，判斷用戶是否登陸當前系統；
1.如果沒有登陸，則停止5秒之后再次判斷，直到用戶登錄系統，顯示用戶登錄，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..."
|
8.取出當前系統上，默認shell為bash的用戶；
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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
|
9.顯示其ID號為偶數的用戶；
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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
|
10.顯示/etc/rc.d/rc.sysinit文件中，其總字符個數大於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.顯示用戶其UID和GID均為偶數的用戶；
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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
|
12.顯示/etc/rc.d/rc.sysinit文件中，其總字符個數大於30且以非#開頭的行；
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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.寫一個腳本，完成如下任務；
1.提示用戶輸入一個磁盤設備文件路徑不存在或不是一個塊設備，則提示用戶重新輸入，知道輸入正確為止，或者輸入quit以9為退出碼結束腳本
2.提示用戶"下面的操作會清空磁盤的數據，並提問是否繼續"
如果用戶給出字符y或yes，則繼續，否則，則提供以8為退出碼結束腳本
3.將用戶指定的磁盤上的分區清空，而后創建兩個分區，大小分別為100M和512M
4.格式化這兩個分區
5.將第一個分區掛載至/mnt/boot目錄，第二個分區掛載至/mnt/sysroot目錄