bash shell 编程练习
1. 创建可执行文件 t2.sh 并打印 "hello world!"
xiluhua@localhost ~ $ mkdir tscripts xiluhua@localhost ~ $ cd tscripts/ xiluhua@localhost ~/tscripts $ echo '#!/bin/bash' >> t2.sh xiluhua@localhost ~/tscripts $ echo 'echo "hello world!"' >>t2.sh xiluhua@localhost ~/tscripts $ chmod +x * xiluhua@localhost ~/tscripts $ ./t2.sh hello world!
2. 运行可执行文件的 3中方法
xiluhua@localhost ~/tscripts $ ./t2.sh hello world! xiluhua@localhost ~/tscripts $ sh t2.sh hello world! xiluhua@localhost ~/tscripts $ /bin/sh t2.sh hello world!
3. 使用变量
xiluhua@localhost ~/tscripts $ name=zhangsan xiluhua@localhost ~/tscripts $ echo $name zhangsan xiluhua@localhost ~/tscripts $ echo ${name} zhangsan xiluhua@localhost ~/tscripts $
变量名外面的花括号是可选的，可加可不加，加花括号是为了帮助解释器识别变量的边界
4. for 循环打印 java c c++ php scala，体会 ${} 的作用
#!/bin/bash for skill in java c c++ php scala;do echo "I am good at $skill" done echo "=======================================" for skill in java c c++ php scala;do echo "I am good at $skillScript" done echo "=======================================" for skill in java c c++ php scala;do echo "I am good at ${skill}Script" done
5. 只读变量，unset 不能取消
xiluhua@localhost ~/tscripts $ name=jack xiluhua@localhost ~/tscripts $ readonly name xiluhua@localhost ~/tscripts $ echo $name jack xiluhua@localhost ~/tscripts $ name=Tom -bash: name: readonly variable xiluhua@localhost ~/tscripts $ unset name -bash: unset: name: cannot unset: readonly variable xiluhua@localhost ~/tscripts $
6. 非只读变量可以取消，取消后打印为空
xiluhua@localhost ~/tscripts $ unname=Jerry xiluhua@localhost ~/tscripts $ unset unname xiluhua@localhost ~/tscripts $ echo $unname
7. 单引号
①. 单引号里的任何字符都原样输出，单引号变量中的变量是无效的； ②. 单引号字符串中不能出现单引号，对单引号使用转义符后也不行 xiluhua@localhost ~ $ name='Leo' xiluhua@localhost ~ $ echo '$name' $name xiluhua@localhost ~ $ echo '$'name' >
8. 双引号
①. 双引号里可以有变量 ②. 双引号里可以出现转义字符 xiluhua@localhost ~ $ echo "I am $name" I am Leo xiluhua@localhost ~ $ echo "\\I am $name \\" \I am Leo \
9. 拼接字符串
xiluhua@localhost ~ $ echo "He is $name" He is Leo xiluhua@localhost ~ $ echo "$name is handsome"! Leo is handsome! xiluhua@localhost ~ $ echo "$name is handsome!" -bash: !": event not found
10. 获取字符串长度
xiluhua@localhost ~ $ echo ${#name} 3
11. 提取字符串
xiluhua@localhost ~ $ echo ${name:0:2}
Le
12. 查找子字符串
xiluhua@localhost ~ $ expr index $name e 2
13. 数组
bash支持一维数组（不支持多维数组），并且没有限定数组的大小。
类似与C语言，数组元素的下标由0开始编号。获取数组中的元素要利用下标，下标可以是整数或算术表达式，其值应大于或等于0。
14. 声明数组并打印一
xiluhua@localhost ~ $ arr=(a b c) xiluhua@localhost ~ $ echo $arr a xiluhua@localhost ~ $ echo ${arr[0]} a xiluhua@localhost ~ $ echo ${arr[2]} c xiluhua@localhost ~ $ echo ${arr[@]} a b c
15. 声明数组并打印二
xiluhua@localhost ~ $ arr=() xiluhua@localhost ~ $ echo ${arr[@]} xiluhua@localhost ~ $ arr[0]=x xiluhua@localhost ~ $ echo ${arr[0]} x xiluhua@localhost ~ $ arr[1]=y xiluhua@localhost ~ $ arr[2]=z xiluhua@localhost ~ $ echo ${arr[@]} # 打印数组全部内容 x y z xiluhua@localhost ~ $ echo ${arr[*]} # 打印数组全部内容 x y z
16. 获取数组长度
xiluhua@localhost ~ $ echo ${#arr[@]} 3
17. 获取数组单个元素的长度
xiluhua@localhost ~ $ arr[3]=yes xiluhua@localhost ~ $ echo ${arr[3]} yes xiluhua@localhost ~ $ echo ${#arr[3]} 3
18. shell 传递参数
#!/bin/bash # auth: xiluhua # date: 2017-01-14 echo 'args 0,file name: '$0 echo 'args 1: '$1 echo 'args 2: '$2 echo 'args 3: '$3
19. 特殊字符
#!/bin/bash # auth: xiluhua # date: 2017-01-14 echo 'shell exercise' echo 'first arg: '$1 echo 'args total number: '$# echo 'args are: '$* echo 'current process id: '$$ echo 'the last proess id run in the background: '$! echo 'args are: '$@ echo 'shell options: '$- echo 'command run status: '$?
20. $* 与$@ 的区别
相同点：都是引用所有参数。 不同点：只有在双引号中体现出来。假设在脚本运行时写了三个参数 1、2、3，， "*" 等价于 "1 2 3"（传递了一个参数）， "@" 等价于 "1" "2" "3"（传递了三个参数）
21. $* 与$@ 的区别实例
#!/bin/bash # auth: xiluhua # date: 2017-01-14 echo '--- $* DEMO ---' for i in "$*";do echo 'i: '$i done echo '--- $@ DEMO ---' for i in "$@";do echo 'i: '$i done
22. 新建可执行文件
sbash='#!/bin/bash' sauth='# auth: xiluhua' sdate="# date: $(date +%Y-%m-%d)" shead="$sbash\n$sauth\n$sdate"
23. expr
原生bash不支持简单的数学运算，但是可以通过其他命令来实现，例如 awk 和 expr，expr 最常用。
expr 是一款表达式计算工具，使用它能完成表达式的求值操作。
- 表达式和运算符之间要有空格，例如 2+2 是不对的，必须写成 2 + 2，这与我们熟悉的大多数编程语言不一样。
- 完整的表达式要被 ` ` 包含，注意这个字符不是常用的单引号，在 Esc 键下边。
例如，两个数相加(注意使用的是反引号 ` 而不是单引号 ')：
xiluhua@localhost ~/tscripts $ expr 2 + 2 4 xiluhua@localhost ~/tscripts $ sum=`expr 2 + 2` xiluhua@localhost ~/tscripts $ echo $sum 4
24. expr 加减乘除运算
xiluhua@localhost ~/tscripts $ a=20 xiluhua@localhost ~/tscripts $ b=10 xiluhua@localhost ~/tscripts $ sum=`expr $a + $b` xiluhua@localhost ~/tscripts $ echo $sum 30 xiluhua@localhost ~/tscripts $ diff=`expr $a - $b` xiluhua@localhost ~/tscripts $ echo $diff 10 xiluhua@localhost ~/tscripts $ prod=`expr $a \* $b` xiluhua@localhost ~/tscripts $ echo $prod 200 xiluhua@localhost ~/tscripts $ odd=`expr $a / $b` xiluhua@localhost ~/tscripts $ echo $odd 2
25. expr 和算术运算符实例
注意：乘号(*)前边必须加反斜杠(\)才能实现乘法运算；
#!/bin/bash # auth: xiluhua # date: 2017-01-14 a=20 b=10 echo '--- expr DEMO ---' echo 'a=20' echo 'b=10' sum=`expr $a + $b` dif=`expr $a - $b` pro=`expr $a \* $b` odd=`expr $a / $b` echo 'sum: '$sum echo 'dif: '$dif echo 'pro: '$pro echo 'odd: '$odd if [ $a == $b ] then echo 'a equal b' fi if [ $a != $b ] then echo a "don't equal b" fi
26. 逻辑运算符
#!/bin/bash # auth: xiluhua # date: 2017-01-14 a=20 b=10 echo '--- bool operators DEMO ---' echo 'a=20' echo 'b=10' if [ $a != $b ] then echo 'a !equal b' else echo 'a equal b' fi if [ $a -gt $b -a $a -lt 30 ] then echo 'a gt 10 but lt 30' else echo '! ag 10 but lt 30' fi if [ $b -eq 10 -o $b -gt 9 ] then echo 'b ge 9' else echo '!b ge 9' fi
26. 字符串运算符
#!/bin/bash # auth: xiluhua # date: 2017-01-14 a=abc b=efg c='' echo "--- string DEMO ---" echo "a=abc" echo "b=efg" if [ $a = $b ] then echo "a eq b" else echo "a !eq b" fi if [ $a != $b ] then echo "a !eq b" else echo "a eq b" fi if [ -z $a ] then echo "a's length is 0" else echo "a's length is ${#a}" fi if [ -z $c ] then echo "c's length is 0" else echo "c's length is ${#c}" fi if [ -n $a ] then echo "a's length is ${#a}" else echo "a's length is 0" fi if [ -n $c ] then echo "c's length is ${#c}" else echo "c's length is 0" fi if [ $a ] then echo "a's length is ${#a}" else echo "a's length is 0" fi if [ $c ] then echo "c's length is ${#c}" else echo "c's length is 0" fi
27. 关系运算符
#!/bin/bash # auth: xiluhua # date: 2017-01-14 file='/home/xiluhua/tscripts' echo '--- file test operators DEMO ---' echo $file if [ -e $file ] then echo "$file is exist" else echo "$file is !exist" fi if [ -d $file ] then echo "$file is a directory" fi if [ -f $file ] then echo "$file is a file" fi if [ -s $file ] then echo "$file is empty" fi if [ -r $file ] then echo "$file is readable" else echo "$file is !readable" fi if [ -w $file ] then echo "$file is writable" else echo "$file is !writable" fi if [ -x $file ] then echo "$file is excecutable" else echo "$file is !excecutable" fi
28. echo 显示转义字符
echo "\"It is a test\""
29. echo 开启换行
xiluhua@localhost ~/tscripts $ echo -e "Tom \n is from China" Tom is from China
30. echo 不开启换行
#!/bin/bash # auth: xiluhua # date: 2017-01-14 echo -e "Tom is from China, \c" echo "he is programmer."
31. printf
#!/bin/bash # auth: xiluhua # date: 2017-01-14 printf "%-10s %-8s %-10s\n" name gender weight[kg] printf "%-10s %-8s %-4.2f\n" Jack male 68.1234 printf "%-10s %-8s %-4.2f\n" Tom male 78.6512 printf "%-10s %-8s %-4.2f\n" Susan female 80
32. printf
%s %c %d %f都是格式替代符 %-10s 指一个宽度为10个字符（-表示左对齐，没有则表示右对齐），任何字符都会被显示在10个字符宽的字符内，如果不足则自动以空格填充，超过也会将内容全部显示出来。 %-4.2f 指格式化为小数，其中.2指保留2位小数。
33. while (1)
#!/bin/bash # auth: xiluhua # date: 2017-01-15 n1=$1 echo '--- while DEMO ---' echo 'n1=$n1' while (( $n1 <= 5 )) do echo $n1 n1=`expr $n1 + 1` # 等同于 let 'n1++' done
34. while (2)
#!/bin/bash # auth: xiluhua # date: 2017-01-15 while true do read -p 'please input a film: ' film if [ -z $film ] then echo > /dev/null else if [ $film = 'q' ] then exit fi if [ $film = 'ironman' ] then echo $film' is a good film!' exit 0; else echo 'this film is not good enough' fi fi done
35. until
#!/bin/bash # auth: xiluhua # date: 2017-01-15 n1=$1 if [ -z $n1 ] then n1=1 fi echo 'n1='$1 until test $[n1] -gt 2 do echo $n1 let 'n1++' done
36. case (1)
#!/bin/bash # auth: xiluhua # date: 2017-01-15 while true do read -p 'please enter a num:' n1 case $n1 in 1|2|3|4|5) echo 'u enter:'$n1 ;; *) echo 'game over!' break esac done
37. case (2)
#!/bin/bash # auth: xiluhua # date: 2017-01-15 while true do read -p 'please enter a num:' n1 case $n1 in 1|2|3|4|5) echo 'u enter:'$n1 ;; *) continue esac done
38. funtion
#!/bin/bash # auth: xiluhua # date: 2017-01-15 first(){ echo 'i am handsome!' } first
39. function 传参
#!/bin/bash # auth: xiluhua # date: 2017-01-15 second(){ echo 'first args:'$1 echo 'second args:'$2 } second 1 2
40. 重定向
标准输入文件(stdin)：stdin的文件描述符为0，Unix程序默认从stdin读取数据。
标准输出文件(stdout)：stdout 的文件描述符为1，Unix程序默认向stdout输出数据。
标准错误文件(stderr)：stderr的文件描述符为2，Unix程序会向stderr流中写入错误信息。
41. 输出错误重定向
xiluhua@localhost ~/t2scripts $ cat echo 2>>err.log xiluhua@localhost ~/t2scripts $ less err.log cat: echo: No such file or directory
42. 2&>1
find /etc -name passwd 2>&1 | less > e.log
43. 将标准输出重定向到一个文件的同时并在屏幕上显示
格式：<command> 2>&1 | tee <logfile> xiluhua@localhost ~/t2scripts $ id das 2>&1 |tee logfile id: das: No such user xiluhua@localhost ~/t2scripts $ less logfile id: das: No such user logfile (END)
44. Here Document
xiluhua@localhost ~/t2scripts $ wc -l << EOF > 1 > 2 > 3 > EOF 3
45. function 引用
#!/bin/bash # auth: xiluhua # date: 2017-01-15 . ./t21.sh second 3 4
46. 为变量设定默认值
[ -z "$name" ] && name="obama"
47. 测试脚本语法
bash -n scripts.sh
48. 1加到100
#!/bin/bash # auth: xiluhua # date: 2017-03-19 declare -i sum=0 for i in {1..100};do sum=$[$sum+$i] if [ $i -eq 100 ];then echo $sum fi done
