一 什么是kernel , shell ，shell script
Kernel是linux管理整个电脑硬件系统，并向上层应用提供接口来调用硬件。
shell是用户和linux交互来控制kenel的一种应用程序。
系统中的shell类型有
[root@localhost ~]# cat /etc/shells /bin/sh /bin/bash /sbin/nologin /usr/bin/sh /usr/bin/bash /usr/sbin/nologin /bin/tcsh /bin/csh
查看当前使用的shell
[root@localhost ~]# echo $SHELL /bin/bash
shell script 是把命令堆砌在一起，来实现特定功能的程序化脚本。
二 变量：可变化的量，命名内存空间
bash环境：
本地变量：当前shell进程；
环境变量：当前shell进程及其子进程；
局部变量：某个函数执行过程；
位置参数变量：在脚本中引用传递给脚本的参数；在函数中引用传递给函数的参数；
特殊变量：$?, $*, $@, $#, $$
定义变量
name=value
name: 变量名
=：赋值符号
value：值
变量名：只能包含数字、字母和下划线；且不能以数字开头；
引用变量：${name}, $name
[root@localhost ~]# x=myx #设置x的值为myx [root@localhost ~]# echo $x #显示x的值，使用$引用 myx 10x=myx #以数字开头命名变量，显示错误 bash: 10x=myx: 未找到命令...
引用：
弱引用: "", 其内部的变量引用会被替换为变量值；
强引用：''，其变量的变量引用会保持原有字符；
命令引用：`COMMAND`, $(COMMAND)，引用命令的执行结果；
[root@localhost ~]# x=myx [root@localhost ~]# echo "x is $x" #弱引用，$x替换 x is myx [root@localhost ~]# echo 'x is $x' #强引用，$x不替换 x is $x [root@localhost ~]# uname -r 3.10.0-229.el7.x86_64 [root@localhost ~]# cd /lib/modules/`uname -r`/kernel #命令替换 `uname -r`/ 替换为3.10.0-229.el7.x86_64 [root@localhost kernel]# pwd /lib/modules/3.10.0-229.el7.x86_64/kernel
声明为整型：
declare -i name[=value]
let name=value
生命周期：
创建
销毁：
自动销毁：shell进程终止；
手动销毁：unset name
[root@localhost ~]# test=mytest #设置变量 [root@localhost ~]# echo $test #变量可以显示 mytest [root@localhost ~]# unset test #销毁变量 [root@localhost ~]# echo $test #在次echo，显示为空
环境变量：
被“导出”的本地变量
export name[=value]
declare -x name[=value]
累加变量 『PATH="$PATH":/home/bin』或『PATH=${PATH}:/home/bin』
查看所有环境变量：env, printenv, export
三 命令状态结果：
bash进程用于追踪执行的命令成功与否的状态：
0: 成功
1-255：失败
特殊变量：
$?：上一条命令的执行状态结果；
布尔型：
“真”：成功
“假”：失败
自定义脚本的状态结果：
exit [n]
注意：脚本中任何位置执行了exit命令即会终止当前shell进程；
[root@localhost ~]# cat /etc/passwd [root@localhost ~]# echo $? 0 [root@localhost ~]# vim test.sh #!/bin/bash cat /etc/passwd exit 3 [root@localhost ~]# bash test.sh [root@localhost ~]# echo $? 3
四 条件测试：
界定程序执行环境；
(1) 根据运行的命令的状态结果；
(2) 测试表达式
test EXPRESSION
[ EXPRESSION ]
` EXPRESSION `
整数测试：隐含着做数值大小比较，所以不要给变量引用加引用；
$A -gt $B：是否大于；是则为“真”，否则为“假”；
$A -ge $B: 是否大于等于；
$A -lt $B：是否小于；
$A -le $B: 是否小于等于；
$A -eq $B: 是否等于；
$A -ne $B：是否不等于；
[root@localhost ~]# A=10 [root@localhost ~]# B=20 [root@localhost ~]# C=10 [root@localhost ~]# test $A -gt $B #A 大于B [root@localhost ~]# echo $? #假 1 [root@localhost ~]# test $A -lt $B #A小于B [root@localhost ~]# echo $? #真 0 [root@localhost ~]# [ $A -lt $B ] #用中括号测试 [root@localhost ~]# echo $? 0 [root@localhost ~]# [[ $A -lt $B ]] #双中知号同样可以测试 [root@localhost ~]# echo $? 0 [root@localhost ~]# test $A -lt $C #A小于C [root@localhost ~]# echo $? #假 1 [root@localhost ~]# test $A -ge $C #A大于等于C [root@localhost ~]# echo $? #真 0 [root@localhost ~]# test $A -le $C #A小于等于C [root@localhost ~]# echo $? #真 0 [root@localhost ~]# test $A -eq $C #A等于C [root@localhost ~]# echo $? #真 0 [root@localhost ~]# test $A -ne $C # A不等于C [root@localhost ~]# echo $? #假 1 [root@localhost ~]# test $A -ne $B #A不等于B [root@localhost ~]# echo $? #真 0
字符串测试：ASCII数值越大，字符比较时其值越大；
"$A" > "$B"：是否大于；
"$A" < "$B"：是否小于；
"$A" == "$B"：是否等于；
"$A" != "$B"：是否不等于；
-z "$A"：是否为空；空则为“真”，否则为“假”
-n "$A"：是否不空；不空则“真”，空则为“假”
注意： 字符串测试应该使用双中括号 ` EXPRESSION `
[root@localhost ~]# A=pass [root@localhost ~]# B=pbaa [root@localhost ~]# C=pass [root@localhost ~]# test "$A">"$B" #pa 在pb前面 ，所以A大于B [root@localhost ~]# echo $? 0 [root@localhost ~]# test "$A"=="$C" [root@localhost ~]# echo $? 0
文件测试：测试文件的存在性以及属性；
-e $file: 是否存在；存在则为“真”，否则为“假”；
-a $file: 同上；
-f $file：文件是否存在且为普通文件；
-d $file：文件是否存在且为目录；
-h $file：是否存在且为符号链接文件；
-L $file: 同上
-b $file：是否存在且为块设备文件；
-c $file：是否存在且为字符设备文件；
-S $file：是否存在且为套接字文件；
-p $file: 是否存在且为管道文件；
-r $file: 当前用户对文件是否拥有读权限；
-w $file：当前用户对文件是否拥有写权限；
-x $file：当前用户对文件是否拥有执行权限；
-u $file：文件是否拥有SUID权限；
-g $file：文件是否拥有SGID权限；
-k $file：文件是否拥有sticky权限；
-O $file: 当前用户是否为指定文件的属主；
-G $file: 当前用户是否为指定文件的属组；
双目操作符：
$file1 -nt $file2: file1是否新于file2, file1的最近一次的修改时间戳是否晚于file2的；
$file1 -ot $file2: file1是否旧于file2, file1的最近一次的修改时间戳是否早于file2的；
$file1 -ef $file2：file1与file2是否指向了同一个inode；测试二者是否为同一个文件的硬链接；
[root@localhost ~]# mkdir /test [root@localhost ~]# cd /test [root@localhost test]# touch test1.txt [root@localhost test]# test -e test1.txt #测试是否存在文件test1.txt [root@localhost test]# echo $? #真 0 [root@localhost test]# test -e test2.txt #测试是否存在文件test2.txt [root@localhost test]# echo $? #假 1 [root@localhost test]# test -a test1.txt #测试是否存在文件test1.txt [root@localhost test]# echo $? #真 0 [root@localhost test]# test -f test1.txt #测试test1.txt是否为普通文件 [root@localhost test]# echo $? 0 [root@localhost test]# test -O test1.txt #测试test1.txt的属主是否和当前用户一至 [root@localhost test]# echo $? #真 0 [root@localhost test]# test -G test1.txt #测试test1.txt的属主是否和当前用户一至 [root@localhost test]# echo $? #真 0 [root@localhost test]# useradd cenos [root@localhost test]# [root@localhost test]# su - cenos [cenos@localhost ~]$ cd /test [cenos@localhost test]$ test -O test1.txt #测试test1.txt的属主是否和当前用户一至 [cenos@localhost test]$ echo $? #假 1 [cenos@localhost test]$ test -G test1.txt #测试test1.txt的属主是否和当前用户一至 [cenos@localhost test]$ echo $? #假 1 [root@localhost test]# touch test2.txt [root@localhost test]# test test2.txt -nt test1.txt #测试test2.txt修改时间是否晚于text1.txt [root@localhost test]# echo $? #真 0 [root@localhost test]# test test2.txt -ot test1.txt #测试test2.txt修改时间是否早于text1.txt [root@localhost test]# echo $? #假 1 [root@localhost test]# ln test1.txt test3.txt [root@localhost test]# test test3.txt -ef test1.txt #测试test3.txt test1.txt是否为同一文件硬链接 [root@localhost test]# echo $? #真 0
五 选择执行 if else fi
if condition
then
condition 判断状态为直，$?值为0
执行 commands
else
condition 判断状态为假，$?值为1-255
执行 commands
fi
或者
if condition
then
condition 判断状态为直，$?值为0
执行 commands
elif condition1
then
condition1 判断状态为直，$?值为0
执行 commands
elif condition2
then
condition2 判断状态为直，$?值为0
执行 commands
else
condition 判断状态为假，$?值为1-255
执行 commands
fi
例如
[root@localhost test]# vim test.sh echo "Please choose one" echo "1.show test1" echo "2.show test2" echo -n "Select your os choice [1 or 2]? " read test if [ $test -eq 1 ] ; then echo "choose (test1)" else if [ $test -eq 2 ] ; then echo "choose (test2)" else echo "choose else " fi fi [root@localhost test]# bash test.sh Please choose one 1.show test1 2.show test2 Select your os choice [1 or 2]? 1 choose (test1) [root@localhost test]# bash test.sh Please choose one 1.show test1 2.show test2 Select your os choice [1 or 2]? 2 choose (test2) [root@localhost test]# bash test.sh Please choose one 1.show test1 2.show test2 Select your os choice [1 or 2]? 3 choose else [root@localhost test]# bash test.sh Please choose one 1.show test1 2.show test2 Select your os choice [1 or 2]? test.sh: line 7: [: -eq: unary operator expected test.sh: line 13: [: -eq: unary operator expected choose else
六 脚本参数(位置参数变量):
# ./script.sh /etc/fstab /etc/grub2.cfg
$0 $1 $2
位置参数变量：$1, $2, ...
${10}
特殊变量：
$?: 命令的状态结果；
$#: 传递给脚本或函数的参数的个数；
$*和$@: 引用传递给脚本或函数的参数列表；
shift [n]：轮替
[root@localhost test]# vim scrip.sh #!/bin/bash echo "Total number of command line argument are $#" echo "$0 is script name" echo "$1 is first argument" echo "$2 is second argument" echo "All of them are :- $* or $@" [root@localhost test]# bash scrip.sh test1 test2 test3 test4 Total number of command line argument are 4 scrip.sh is script name test1 is first argument test2 is second argument All of them are :- test1 test2 test3 test4 or test1 test2 test3 test4
[root@localhost test]# vim scrip2.sh echo "$1 is first argument" shift echo "$1 is second argument" shift echo "$1 is third argument" [root@localhost test]# bash scrip2.sh test1 test2 test3 test4 test1 is first argument test2 is second argument test3 is third argument
七 循环
循环 for
for { variable } in { list }
do
执行命令，直到list到最后一个
done
LIST的生成方法：
(1) 整数列表
(a) {start..end} {1..10}
(b) $(seq [start `step` end) seq 0 2 10 (0 2 4 6 8 10)
(2) 直接给出列表 user1 user2 user3 user4 user5
(3) glob /var/log/*
(4) 命令生成 $(cut -d: -f1 /etc/passwd)
[root@localhost test]# vim for1.sh for i in 1 2 3 4 5 do echo "Welcome $i times" done [root@localhost test]# bash for1.sh Welcome 1 times Welcome 2 times Welcome 3 times Welcome 4 times Welcome 5 times
循环 while, until
while [ condition ]
do
command1
command2
....
done
while循环
进入条件：当CONDITION为“真”；
退出条件：当CONDITION为“假”；
until [ condition ]
do
command1
command2
....
done
unitl循环
进入条件：当CONDITION为“假”时
退出条件：当CONDITION为“真”时
[root@localhost test]# vim testwhile.sh #!/bin/bash if [ $# -eq 0 ] then echo "Error - please input like bash testwhile.sh no." exit 1 fi n=$1 i=1 while [ $i -le 10 ] do echo "$n * $i = `expr $i \* $n`" i=`expr $i + 1` done [root@localhost test]# bash testwhile.sh Error - please input like bash testwhile.sh no. [root@localhost test]# bash testwhile.sh 5 5 * 1 = 5 5 * 2 = 10 5 * 3 = 15 5 * 4 = 20 5 * 5 = 25 5 * 6 = 30 5 * 7 = 35 5 * 8 = 40 5 * 9 = 45 5 * 10 = 50
循环 case
case $variable in
pattern1) command
...
command;;
pattern2) command
...
command;;
patternN) command
...
command;;
*) command
...
command;;
esac
八 函数
定义方法：
(1) function f_name
{
函数体
}
(2) f_name()
{
函数体
}
调用函数：
f_name [argu1, argu2, ...]
九 sed & awk
正在总结 跳转
练习：
5、写一个脚本：如果某路径不存在，则将其创建为目录；否则显示其存在，并显示内容类型；（不要怀疑，就是这么简单）
mkdir /test [root@localhost test]# vim /test/homework1.sh #!/bin/bash if [ $# -lt 1 ] then echo "usage: command file" exit 1 fi if [ -e $1 ] then echo "file exist" file $1 else echo " create fold $1" mkdir -p $1 fi [root@localhost test]# cd /test/ [root@localhost test]# bash homework1.sh /test/test create fold /test/test [root@localhost test]# bash homework1.sh /test/test file exist /test/test: directory [root@localhost test]# touch /test/test/test.txt [root@localhost test]# bash homework1.sh /test/test/test.txt file exist /test/test/test.txt: empty
6、写一个脚本，完成如下功能；判断给定的两个数值，孰大孰小；给定数值的方法：脚本参数，命令交互；（使用read，依然如此简单）
a脚本参数
[root@localhost test]# vim homework2.sh else echo "$1 is equal $2" #!/bin/bash if [ $# -lt 2 ] then echo "usage: command data1 data2" exit 1 fi if [ $1 -gt $2 ] then echo "$1 is big than $2" else if [ $1 -eq $2 ] then echo "$1 is equal $2" else echo "$1 is small than $2" fi fi [root@localhost test]# bash homework2.sh 10 20 10 is small than 20 [root@localhost test]# bash homework2.sh 20 10 20 is big than 10 [root@localhost test]# bash homework2.sh 20 usage: command data1 data2
b命令交互 read
[root@localhost test]# vim homework3.sh #!/bin/bash read -p "Plz enter two integer: " -t 20 num1 num2 if [ $num1 -gt $num2 ] then echo "$num1 is big than $num2" else if [ $num1 -eq $num2 ] then echo "$num1 is equal $num2" else echo "$num1 is small than $num2" fi fi [root@localhost test]# bash homework3.sh Plz enter two integer: 10 20 10 is small than 20 [root@localhost test]# bash homework3.sh Plz enter two integer: 20 10 20 is big than 10 [root@localhost test]# bash homework3.sh Plz enter two integer: 10 10 10 is equal 10
7、求100以内所有奇数之和（至少用3种方法。是的这是我们的作业^_^）
方法a for 判断
[root@localhost test]# vim sum100.1.sh
#!/bin/bash
declare -i sum=0
for i in {1..100}
do
if [ $[$i%2] -eq 1 ]
then
sum=$[$sum+$i]
fi
done
echo "Sum is : $sum"
[root@localhost test]# bash sum100.1.sh
Sum is : 2500
方法b for list步进 [root@localhost test]# vim sum100.2.sh #!/bin/bash declare -i sum=0 for i in $(seq 1 2 100) do sum=$(($sum+$i)) done echo "Sum is : $sum" [root@localhost test]# bash sum100.2.sh Sum is : 2500
方法c while 判断 [root@localhost test]# vim sum100.3.sh declare -i sum=0 declare -i i=0 while [ $i -le 100 ] do if [ $[$i%2] -eq 1 ] then let sum+=$i fi let i++ done echo "sum is : $sum" [root@localhost test]# bash sum100.3.sh sum is : 2500
8、写一个脚本实现如下功能：
(1) 传递两个文本文件路径给脚本；
(2) 显示两个文件中空白行数较多的文件及其空白行的个数；
(3) 显示两个文件中总行数较多的文件及其总行数；
[root@localhost test]# vim countspace.sh if [ ! -f $1 ] then echo "$1 is not a common file " exit 1 fi if [ ! -f $2 ] then echo "$2 is not a common file" exit 1 fi file1_line=`cat $1 | wc -l` echo $file1_line file2_line=`cat $2 | wc -l` echo $file2_line if [ $file1_line -eq $file2_line ] then echo "both file have $file1_line lines" elif [ $file1_line -gt $file2_line ] then echo " $1 have $file1_line lines more than $2 have $file2_line" else echo " $2 have $file2_line lines more than $1 have $file1_line" fi file1_spaceline=`grep "^$" $1 | wc -l` echo $file1_spaceline file2_spaceline=`grep "^$" $2 | wc -l` echo $file2_spaceline if [ $file1_spaceline -eq $file2_spaceline ] then echo "both file have $file1_spaceline lines" elif [ $file1_spaceline -gt $file2_spaceline ] then echo " $1 have $file1_spaceline space lines more than $2 have $file2_spaceline" else echo " $2 have $file2_spaceline space lines more than $1 have $file1_spaceline" fi [root@localhost test]# bash countspace.sh /test/countspace.sh /etc/fstab 51 16 /test/countspace.sh have 51 lines more than /etc/fstab have 16 9 1 /test/countspace.sh have 9 space lines more than /etc/fstab have 1 [root@localhost test]# bash countspace.sh /test/countspace.sh useage: scrip filepath1 filepath2 [root@localhost test]# bash countspace.sh /test/countspace.sh /etc /etc is not a common file [root@localhost test]# bash countspace.sh useage: scrip filepath1 filepath2
9、写一个脚本
(1) 提示用户输入一个字符串；
(2) 判断：
如果输入的是quit，则退出脚本；
否则，则显示其输入的字符串内容；
[root@localhost test]# vim quitscript.sh #!/bin/bash read -p "please input a string:" -t 10 str1 if [[ -z "$str1" ]] then echo "please input something" elif [[ "$str1" == "quit" ]] then exit 0 else echo "you inupt is $str1" fi [root@localhost test]# bash quitscript.sh please input a string: please input something [root@localhost test]# bash quitscript.sh please input a string:test you inupt is test [root@localhost test]# bash quitscript.sh please input a string:quit
10、写一个脚本，打印2^n表；n等于一个用户输入的值；（不好意思，我调皮了）
[root@localhost test]# vim power2.sh #!/bin/bash if [ $# -lt 1 ] then echo "usage: command number" exit 1 fi if [ $1 -le 0 ] then echo "please input a number big the 0" elif [ $1 -eq 1 ] then echo "2x1=2" else sum=2 echo -n "2" for i in `seq 2 $1` do let sum*=2 echo -n "X2" done echo "=$sum" fi [root@localhost test]# bash power2.sh usage: command number [root@localhost test]# bash power2.sh 0 please input a number big the 0 [root@localhost test]# bash power2.sh 1 2x1=2 [root@localhost test]# bash power2.sh 2 2X2=4 [root@localhost test]# bash power2.sh 3 2X2X2=8 [root@localhost test]# bash power2.sh 4 2X2X2X2=16 [root@localhost test]# bash power2.sh 8 2X2X2X2X2X2X2X2=256 [root@localhost test]# bash power2.sh 32 2X2X2X2X2X2X2X2X2X2X2X2X2X2X2X2X2X2X2X2X2X2X2X2X2X2X2X2X2X2X2X2=4294967296
11、写一个脚本，写这么几个函数：函数1、实现给定的两个数值的之和；函数2、取给定两个数值的最大公约数；函数3、取给定两个数值的最小公倍数；关于函数的选定、两个数值的大小都将通过交互式输入来提供。
[root@localhost test]# vim testfun.sh
#!/bin/bash
while [ ture ]
do
echo "calcule usage is script operater number1 number2"
echo "operater have 3 methord:"
echo -e "1.summary usage example: \033[31msum number1 number2\033[0m"
echo -e "2.Least Common Multiple (LCM) usage example: \033[31mlcm number1 number2\033[0m"
echo -e "3.Greatest Common Divisor(GCD) usage example: \033[31mgcd number1 number2\033[0m"
echo -e "inupt \033[31mquit\033[0m this script will exit"
read -p "please input select: " op num1 num2
function testsum()
{
clear
echo "================================================="
echo -e "\033[31msum is `expr $num1 \* $num2` \033[0m"
echo "================================================="
}
function gongyue()
{
a=$num1
local b=$num2
local tmp=0
if [ $a -lt $b ]
then
tmp=$a
a=$b
b=$tmp
fi
while [ $b -ne 0 ]
do
tmp=$(($a%$b))
a=$b
b=$tmp
done
clear
echo "================================================="
echo -e "\033[31mgongyue is $a\033[0m"
echo "================================================="
}
function gongbei()
{
clear
echo "================================================="
echo -e "\033[31mgongbei is $(($num1*$num2/$a))\033[0m"
echo "================================================="
}
if [[ "$op" == "quit" ]]
then
break
exit 0
elif [[ "$op" == "sum" ]]
then
testsum num1 num2
elif [[ "$op" == "lcm" ]]
then
gongyue num1 num2
elif [[ "$op" == "gcd" ]]
then
gongbei num1 num2
else
echo "input error"
fi
done
[root@localhost test]# bash testfun.sh
calcule usage is script operater number1 number2
operater have 3 methord:
1.summary usage example: sum number1 number2
2.Least Common Multiple (LCM) usage example: lcm number1 number2
3.Greatest Common Divisor(GCD) usage example: gcd number1 number2
inupt quit this script will exit
please input select: sum 1397 2413
=================================================
sum is 3370961
=================================================
calcule usage is script operater number1 number2
operater have 3 methord:
1.summary usage example: sum number1 number2
2.Least Common Multiple (LCM) usage example: lcm number1 number2
3.Greatest Common Divisor(GCD) usage example: gcd number1 number2
inupt quit this script will exit
please input select: quit
please input select: lcm 1397 2413
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gongyue is 127
=================================================
calcule usage is script operater number1 number2
operater have 3 methord:
1.summary usage example: sum number1 number2
2.Least Common Multiple (LCM) usage example: lcm number1 number2
3.Greatest Common Divisor(GCD) usage example: gcd number1 number2
inupt quit this script will exit
please input select: gcd 1397 2413
=================================================
gongbei is 26543
=================================================
calcule usage is script operater number1 number2
operater have 3 methord:
1.summary usage example: sum number1 number2
2.Least Common Multiple (LCM) usage example: lcm number1 number2
3.Greatest Common Divisor(GCD) usage example: gcd number1 number2
inupt quit this script will exit
please input select: quit