收藏！一篇教会你写90%的shell脚本！

{"type":"doc","content":[{"type":"blockquote","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"在公司项目的开发过程中，需要编写shell脚本去处理一个业务，在编写过程中发现自身对shell脚本的知识不够完善，顾整理一下，本文章主要内容来自"},{"type":"link","attrs":{"href":"https://www.runoob.com/linux/linux-shell.html","title":""},"content":[{"type":"text","text":"菜鸟教程"}]},{"type":"text","text":" , 也添加了一些知识点"}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"blockquote","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"看完这边文章应该就可以独立完成大部分脚本得编写"}]}]},{"type":"heading","attrs":{"align":null,"level":4},"content":[{"type":"text","text":"shell脚本？"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong"}],"text":"在说什么是shell脚本之前，先说说什么是shell。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"shell是外壳的意思，就是操作系统的外壳。我们可以通过shell命令来操作和控制操作系统，比如Linux中的Shell命令就包括ls、cd、pwd等等。总结来说，Shell是一个命令解释器，它通过接受用户输入的Shell命令来启动、暂停、停止程序的运行或对计算机进行控制。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"shell 是一个应用程序，它连接了用户和 Linux 内核，让用户能够更加高效、安全、低成本地使用 Linux 内核，这就是 Shell 的本质。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"shell 本身并不是内核的一部分，它只是站在内核的基础上编写的一个应用程序。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong"}],"text":"那么什么是shell脚本呢？"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"shell脚本就是由Shell命令组成的执行文件，将一些命令整合到一个文件中，进行处理业务逻辑，脚本不用编译即可运行。它通过解释器解释运行，所以速度相对来说比较慢。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"shell脚本中最重要的就是对shell命令的使用与组合，再使用shell脚本支持的一些语言特性，完成想要的功能。"}]},{"type":"heading","attrs":{"align":null,"level":4},"content":[{"type":"text","text":"注释"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"“# ”开头的就是注释，被编译器忽略"}]},{"type":"bulletedlist","content":[{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"单行注释： # "}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"多行注释： :< readonly name （使用readonly标识后的变量，不可被修改）"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"删除变量： unset name; （删除之后不可访问，删除不掉只读变量）"}]}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong"}],"text":"字符串变量"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"1）单引号"}]},{"type":"bulletedlist","content":[{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"单引号变量"},{"type":"codeinline","content":[{"type":"text","text":"var='test'"}]},{"type":"text","text":" ，只能原样输出，变量无效"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"单引号中不能出现一个单独的单引号，转义也不可以"}]}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"2）双引号"}]},{"type":"bulletedlist","content":[{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"双引号变量"},{"type":"codeinline","content":[{"type":"text","text":"var=\"my name is ${name}\""}]},{"type":"text","text":"，变量有效"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"可出现转义符"}]}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"3）拼接字符串"}]},{"type":"bulletedlist","content":[{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"中间无任何+，之类的字符"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"name=\"this is\"\" my name\"; name=\"this is my name\"; name=\"this\" is \"my name\" 等效"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"name='this is'' my nam'; name='this is my name'; name='this' is 'my name' 等效"}]}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"4）获取字符串长度"}]},{"type":"bulletedlist","content":[{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"在${}中使用“#”获取长度"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"name=\"test\";"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"echo ${#name}; # 输出为4"}]}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"5）提取子字符串"}]},{"type":"bulletedlist","content":[{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"1:4 从第2个开始 往后截取4个字符"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"::4 从第一个字符开始 往后截取4个字符"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"name=\"this is my name\";"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"echo ${name:1:4} #输出 his"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"echo ${name::4} #输出 this"}]}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong"}],"text":"数组"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":" bash只支持一维数组，不支持多维数组"}]},{"type":"bulletedlist","content":[{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"定义数组：array_name=(li wang xiang zhang) （小括号做边界、使用空格分离）"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"单独定义数组的元素： array"},{"type":"text","marks":[{"type":"italic"}],"text":"para[0]=\"w\"; array"},{"type":"text","text":"para[3]=\"s\" （定义时下标不连续也可以）"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"赋值数组元素：array_name[0]=\"zhao\";"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"获取数组元素："}]}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":" * array_name[0]=\"li\""}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":" * array_name[3]=\"zhang\""}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":" * echo ${array_name[0]} # 输出\"li\""}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":" * echo ${array_name[1]} # 输出\" \""}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":" * echo ${array_name[3]} # 输出\"zhang\""}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":" * echo ${array_name[@]} # 输出\"li zhang\" 输出数组所有元素，没有元素的下标省略"}]},{"type":"bulletedlist","content":[{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"取得元素个数：${#array"},{"type":"text","marks":[{"type":"italic"}],"text":"name[@]} 或者 ${#array"},{"type":"text","text":"name[\\*]}"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"取得单个元素长度：${#array_name[1]}"}]}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"heading","attrs":{"align":null,"level":4},"content":[{"type":"text","text":"参数传递"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"bulletedlist","content":[{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"获取参数值："}]}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":" * $0 ： 固定，代表执行的文件名"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":" * $1 ： 代表传入的第1个参数"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":" * $n ： 代表传入的第n个参数"}]},{"type":"bulletedlist","content":[{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"\\$#：参数个数"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"\\$\\"},{"type":"text","marks":[{"type":"italic"}],"text":"： 以一个单字符串显示所有向脚本传递的参数。如\"$\\"},{"type":"text","text":"\"用「\"」括起来的情况、以\"$1 $2 … $n\"的形式输出所有参数"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"\\$@：与$\\*相同，但是使用时加引号，并在引号中返回每个参数。"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"\\$\\$：脚本运行的当前进程号"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"\\$！：后台运行的最后一个进程的ID"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"\\$?： 显示最后命令的退出状态。0表示没有错误，其他任何值表明有错误。"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"\\$* 与 $@ 区别"}]}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":" * 相同点：都是引用所有参数。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":" "},{"type":"text","marks":[{"type":"italic"}],"text":" 不同点：只有在双引号中体现出来。假设在脚本运行时写了三个参数 1、2、3，，则 \" "},{"type":"text","text":" \" 等价于 \"1 2 3\"（传递了一个参数），而 \"@\" 等价于 \"1\" \"2\" \"3\"（传递了三个参数）。 "}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"heading","attrs":{"align":null,"level":4},"content":[{"type":"text","text":"运算符"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong"}],"text":"算数运算"}]},{"type":"bulletedlist","content":[{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"\\+ 、\\-、\\*、\\ ： 乘号前必须加\\进行转义才可以进行乘法运算"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"加法运算"}]}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":" * val=\\"},{"type":"codeinline","content":[{"type":"text","text":"expr 2 + 2\\"}]},{"type":"text","text":" （使用linux命令expr进行辅助运算） "}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":" * val=$[2+2] （4个空格不是必要的，不同于条件判断）"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":" * val=$((2+2)) "}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong"}],"text":"数字关系运算符"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"关系运算符只支持数字，不支持字符串，除非字符串的值是数字。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"下面假定变量 a 为 10，变量 b 为 20"}]},{"type":"bulletedlist","content":[{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"-eq ：检测两个数是否相等，相等返回 true。\t [ $a -eq $b ] 返回 false。"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"-ne：\t检测两个数是否不相等，不相等返回 true。\t [ $a -ne $b ] 返回 true。"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"-gt：\t检测左边的数是否大于右边的，如果是，则返回 true。 \t[ $a -gt $b ] 返回 false。"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"-lt\t： 检测左边的数是否小于右边的，如果是，则返回 true。\t [ $a -lt $b ] 返回 true。"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"-ge：\t检测左边的数是否大于等于右边的，如果是，则返回 true。 \t[ $a -ge $b ] 返回 false。"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"-le\t： 检测左边的数是否小于等于右边的，如果是，则返回 true。 \t[ $a -le $b ] 返回 true。"}]}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":" "}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":" "},{"type":"text","marks":[{"type":"strong"}],"text":"字符串运算符"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"下表列出了常用的字符串运算符，假定变量 a 为 \"abc\"，变量 b 为 \"efg\"："}]},{"type":"bulletedlist","content":[{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":" =\t：检测两个字符串是否相等，相等返回 true。\t[ $a = $b ] 返回 false。"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"!=\t：检测两个字符串是否相等，不相等返回 true。\t[ $a != $b ] 返回 true。"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"-z\t：检测字符串长度是否为0，为0返回 true。\t[ -z $a ] 返回 false。"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"-n\t：检测字符串长度是否为0，不为0返回 true。\t[ -n \"$a\" ] 返回 true。"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"$ ：检测字符串是否为空，不为空返回 true。\t[ $a ] 返回 true。"}]}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":" "}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":" "},{"type":"text","marks":[{"type":"strong"}],"text":"布尔运算符"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"下表列出了常用的布尔运算符，假定变量 a 为 10，变量 b 为 20："}]},{"type":"bulletedlist","content":[{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":" !\t：非运算，表达式为 true 则返回 false，否则返回 true。\t[ ! false ] 返回 true。"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"-o\t：或运算，有一个表达式为 true 则返回 true。\t[ $a -lt 20 -o $b -gt 100 ] 返回 true。"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"-a\t：与运算，两个表达式都为 true 才返回 true。\t[ $a -lt 20 -a $b -gt 100 ] 返回 false。"}]}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong"}],"text":"逻辑运算符"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"以下介绍 Shell 的逻辑运算符，假定变量 a 为 10，变量 b 为 20:"}]},{"type":"bulletedlist","content":[{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"&&\t：逻辑的 AND\t[[ $a -lt 100 && $b -gt 100 ]] 返回 false"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"\\||\t：逻辑的 OR\t[[ $a -lt 100 || $b -gt 100 ]] 返回 true"}]}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong"}],"text":"文件运算符"}]},{"type":"bulletedlist","content":[{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"-b file\t：检测文件是否是块设备文件，如果是，则返回 true。\t[ -b $file ] 返回 false。"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"-c file\t：检测文件是否是字符设备文件，如果是，则返回 true。\t[ -c $file ] 返回 false。"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"-d file\t：检测文件是否是目录，如果是，则返回 true。\t[ -d $file ] 返回 false。"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"-f file\t：检测文件是否是普通文件（既不是目录，也不是设备文件），如果是，则返回 true。\t[ -f $file ] 返回 true。"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"-g file\t：检测文件是否设置了 SGID 位，如果是，则返回 true。\t[ -g $file ] 返回 false。"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"-k file\t：检测文件是否设置了粘着位(Sticky Bit)，如果是，则返回 true。\t[ -k $file ] 返回 false。"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"-p file\t：检测文件是否是有名管道，如果是，则返回 true。\t[ -p $file ] 返回 false。"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"-u file\t：检测文件是否设置了 SUID 位，如果是，则返回 true。\t[ -u $file ] 返回 false。"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"-r file\t：检测文件是否可读，如果是，则返回 true。\t[ -r $file ] 返回 true。"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"-w file\t：检测文件是否可写，如果是，则返回 true。\t[ -w $file ] 返回 true。"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"-x file ：检测文件是否可执行，如果是，则返回 true。\t[ -x $file ] 返回 true。"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"-s file\t：检测文件是否为空（文件大小是否大于0），不为空返回 true。\t[ -s $file ] 返回 true。"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"-e file\t：检测文件（包括目录）是否存在，如果是，则返回 true。\t[ -e $file ] 返回 true。"}]}]}]},{"type":"heading","attrs":{"align":null,"level":4},"content":[{"type":"text","text":"执行相关"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong"}],"text":"命令替换"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"命令替换与变量替换差不多，都是用来重组命令行的，先完成引号里的命令行，然后将其结果替换出来，再重组成新的命令行。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"执行命令： "}]},{"type":"numberedlist","attrs":{"start":"1","normalizeStart":1},"content":[{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":1,"align":null,"origin":null},"content":[{"type":"text","text":" \\"},{"type":"codeinline","content":[{"type":"text","text":"ls /etc\\"}]},{"type":"text","text":" ： 反引号 （所有的unix系统都支持）"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":2,"align":null,"origin":null},"content":[{"type":"text","text":"$(ls /etc) ： $+() （部分unix系统不支持）"}]}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"多个嵌套使用时，从内向外执行"}]},{"type":"blockquote","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"for file in \\s /etc\\ 或 for file in $(ls /etc) 循环中使用"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"\\"},{"type":"codeinline","content":[{"type":"text","text":"dirname \\$0\\"}]},{"type":"text","text":" 获取脚本文件所在的目录"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"path=$(cd \\"},{"type":"codeinline","content":[{"type":"text","text":"dirname $0\\"}]},{"type":"text","text":";pwd) ： 获取脚本当前所在目录，并且执行cd命令到达该目录，使用pwd获取路径并赋值到path变量"}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong"}],"text":"算术运算"}]},{"type":"numberedlist","attrs":{"start":"1","normalizeStart":1},"content":[{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":1,"align":null,"origin":null},"content":[{"type":"text","text":"$[ ] : 加减乘除,不必添加空格"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":2,"align":null,"origin":null},"content":[{"type":"text","text":"$(( )) ：加减乘除等,不必添加空格"}]}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong"}],"text":"逻辑判断"}]},{"type":"numberedlist","attrs":{"start":"1","normalizeStart":1},"content":[{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":1,"align":null,"origin":null},"content":[{"type":"text","text":"\\[ ] ： 中括号旁边和运算符两边必须添加空格 （可以使用，不推荐）"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":2,"align":null,"origin":null},"content":[{"type":"text","text":"[[ ]]：中括号旁边和运算符两边必须添加空格 （字符串验证时，推荐使用）"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":3,"align":null,"origin":null},"content":[{"type":"text","text":"(()) ： 中括号旁边和运算符两边必须添加空格 （数字验证时，推荐使用）"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":4,"align":null,"origin":null},"content":[{"type":"text","text":"[[]] 和 (()) 分别是[ ]的针对数学比较表达式和字符串表达式的加强版。"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":5,"align":null,"origin":null},"content":[{"type":"text","text":"使用[[ ... ]]条件判断结构，而不是[ ... ]，能够防止脚本中的许多逻辑错误。比如，&&、||、 操作符能够正常存在于[[ ]]条件判断结构中，但是如果出现在[ ]结构中的话，会报错。比如可以直接使用if [[ $a != 1 && $a != 2 ]], 如果不适用双括号, 则为if [ $a -ne 1] && [ $a != 2 ]或者if [ $a -ne 1 -a $a != 2 ]。"}]}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"[[ ]]中增加模式匹配特效；"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"(( ))不需要再将表达式里面的大小于符号转义，除了可以使用标准的数学运算符外，还增加了以下符号"}]},{"type":"image","attrs":{"src":"https://static001.geekbang.org/infoq/d0/d059c812652d73dde1aa387eb3308302.png","alt":"在这里插入图片描述","title":null,"style":null,"href":null,"fromPaste":true,"pastePass":true}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"heading","attrs":{"align":null,"level":4},"content":[{"type":"text","text":"输出"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong"}],"text":"echo"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"仅用于字符串的输出，没有使用printf作为输出的移植性好，建议使用printf"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong"}],"text":"printf"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":">printf 不会像 echo 自动添加换行符，我们可以手动添加 \\n"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":">无大括号，直接以空格分隔"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"bulletedlist","content":[{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"格式："},{"type":"codeinline","content":[{"type":"text","text":"printf format-string [arguments...]"}]},{"type":"text","text":" 其中（format-string: 格式控制字符串、arguments: 参数列表）"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"案例："},{"type":"codeinline","content":[{"type":"text","text":"printf \"%-10s %-8s %-4.2f\\n\" 郭靖 男 66.1234 "}]}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"%s %c %d %f 都是格式替代符"}]}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":" * d：Decimal 十进制整数 对应位置参数必须是十进制整数，否则报错!"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":" * s：String 字符串 对应位置参数必须是字符串或者字符型 否则报错"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":" * c：Char 字符 对应位置参数必须是字符串或者字符型 否则报错"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":" * f：Float 浮点 对应位置参数必须是数字型 否则报错"}]},{"type":"bulletedlist","content":[{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"codeinline","content":[{"type":"text","text":"%-10s"}]},{"type":"text","text":" ： 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。"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"codeinline","content":[{"type":"text","text":"%-4.2f"}]},{"type":"text","text":" ：指格式化为小数，宽度为4个字符，其中"},{"type":"codeinline","content":[{"type":"text","text":".2"}]},{"type":"text","text":"指保留2位小数。"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"转义符："}]}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":" * \\a\t：警告字符，通常为ASCII的BEL字符"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":" * \\b\t：后退"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":" * \\c\t：抑制（不显示）输出结果中任何结尾的换行字符（只在%b格式指示符控制下的参数字符串中有效），而且，任何留在参数里的字符、任何接下来的参数以及任何留在格式字符串中的字符，都被忽略"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":" * \\f\t：换页（formfeed）"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":" * \\n\t：换行"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":" * \\r\t：回车（Carriage return）"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":" * \\t\t：水平制表符"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":" * \\v\t：垂直制表符"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":" * \\\\\t：一个字面上的反斜杠字符"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":" * \\ddd\t：表示1到3位数八进制值的字符。仅在格式字符串中有效"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":" * \\0ddd\t：表示1到3位的八进制值字符"}]},{"type":"heading","attrs":{"align":null,"level":4},"content":[{"type":"text","text":"流程控制"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"和Java、PHP等语言不一样，sh的流程控制不可为空，即if或者else的大括号中无任何语句"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong"}],"text":"if else"}]},{"type":"bulletedlist","content":[{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"if"}]}]}]},{"type":"codeblock","attrs":{"lang":"shell"},"content":[{"type":"text","text":"if condition\nthen\n command1 \n command2\n ...\n commandN \nfi"}]},{"type":"bulletedlist","content":[{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"if else"}]}]}]},{"type":"codeblock","attrs":{"lang":"shell"},"content":[{"type":"text","text":"if condition\nthen\n command1 \n command2\n ...\n commandN\nelse\n command\nfi"}]},{"type":"bulletedlist","content":[{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"if else-if else"}]}]}]},{"type":"codeblock","attrs":{"lang":"shell"},"content":[{"type":"text","text":"if condition1\nthen\n command1\nelif condition2 \nthen \n command2\nelse\n commandN\nfi"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong"}],"text":"for"}]},{"type":"codeblock","attrs":{"lang":"shell"},"content":[{"type":"text","text":"for var in item1 item2 ... itemN\ndo\n command1\n command2\n ...\n commandN\ndone"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong"}],"text":"while"}]},{"type":"bulletedlist","content":[{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"while condition"}]}]}]},{"type":"codeblock","attrs":{"lang":"shell"},"content":[{"type":"text","text":"while condition\ndo\n command\ndone"}]},{"type":"bulletedlist","content":[{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"while 无限循环"}]}]}]},{"type":"codeblock","attrs":{"lang":"shell"},"content":[{"type":"text","text":"while :\ndo\n command\ndone"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong"}],"text":"until"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"until 循环执行一系列命令直至条件为 true 时停止。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"until 循环与 while 循环在处理方式上刚好相反。"}]},{"type":"codeblock","attrs":{"lang":"shell"},"content":[{"type":"text","text":"until condition\ndo\n command\ndone"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong"}],"text":"case"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"Shell case语句为多选择语句。可以用case语句匹配一个值与一个模式，如果匹配成功，执行相匹配的命令。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"case需要一个esac（就是case反过来）作为结束标记，每个case分支用右圆括号，用两个分号表示break，其中“;;”不是跳出循环，是不在去匹配下面的模式"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"case语句格式如下："}]},{"type":"codeblock","attrs":{"lang":"shell"},"content":[{"type":"text","text":"case 值 in\n 模式1)\n command1\n command2\n ...\n commandN\n ;;\n 模式2）\n command1\n command2\n ...\n commandN\n ;;\nesac"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong"}],"text":"跳出循环"}]},{"type":"numberedlist","attrs":{"start":"1","normalizeStart":1},"content":[{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":1,"align":null,"origin":null},"content":[{"type":"text","text":"break ：跳出总循环"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":2,"align":null,"origin":null},"content":[{"type":"text","text":"continue：跳出当前循环，继续下一次循环"}]}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"heading","attrs":{"align":null,"level":4},"content":[{"type":"text","text":"定义函数"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"可以带function fun() 定义，也可以直接fun() 定义,不带任何参数。"}]},{"type":"bulletedlist","content":[{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong"}],"text":"函数定义"}]}]}]},{"type":"codeblock","attrs":{"lang":"shell"},"content":[{"type":"text","text":"[ function ] funname()\n{\n action;\n [return int;]\n}"}]},{"type":"bulletedlist","content":[{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong"}],"text":"参数传递"}]}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":" * 调用函数: fun_name 2 3 4"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":" "},{"type":"text","marks":[{"type":"italic"}],"text":" 函数中使用：和shell取用函数相同 $n $# $"},{"type":"text","text":" $? 或者加上{}"}]},{"type":"codeblock","attrs":{"lang":"shell"},"content":[{"type":"text","text":"funWithParam(){\n echo \"第一个参数为 $1 !\"\n echo \"第二个参数为 $2 !\"\n echo \"第十个参数为 $10 !\"\n echo \"第十个参数为 ${10} !\"\n echo \"第十一个参数为 ${11} !\"\n echo \"参数总数有 $# 个!\"\n echo \"作为一个字符串输出所有参数 $* !\"}\nfunWithParam 1 2 3 4 5 6 7 8 9 34 73\necho $? \\# 判断执行是否成功"}]},{"type":"bulletedlist","content":[{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong"}],"text":"函数返回值"}]}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":" * return字样可存在也可不存在"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":" * return 只能为 return [0-255]，此处的返回可作为函数执行的状态，通过$?获取的便是这个返回值"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":" * 如果不加return ， 则默认最后一条语句的执行状态所为函数执行状态的返回值，如果最后一条语句执行成功，则$?为0，否则不为0"}]},{"type":"bulletedlist","content":[{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong"}],"text":"使用函数返回值"},{"type":"text","text":"（Janusgraph图数据库官方启动服务脚本片段）"}]}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":" * return返回的数字，只是作为函数执行状态的返回值，也就是接下来$?获取的值"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":" * 对于类似于下面的"},{"type":"codeinline","content":[{"type":"text","text":"BIN=\\"}]},{"type":"text","text":"abs_path\\``语句，获取的是函数体内所有的echo、printf输出组合成的一个字符串"}]},{"type":"codeblock","attrs":{"lang":"shell"},"content":[{"type":"text","text":"abs_path() {\n SOURCE=\"${BASH_SOURCE[0]}\"\n while [ -h \"$SOURCE\" ]; do\n DIR=\"$( cd -P \"$( dirname \"$SOURCE\" )\" && pwd )\"\n SOURCE=\"$(readlink \"$SOURCE\")\"\n [[ $SOURCE != /* ]] && SOURCE=\"$DIR/$SOURCE\"\n done\n echo \"test\" \n echo \"$( cd -P \"$( dirname \"$SOURCE\" )\" && pwd )\" \n # 此函数的两个echo输出会组合成一个字符串作为下述BIN的值\n}\n\nBIN=`abs_path` # BIN赋值函数返回值，如果没有return，则函数中所有的echo、printf输出组合成一个字符串传入BIN\npath=${BIN}/nodetool # 可直接使用"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"heading","attrs":{"align":null,"level":4},"content":[{"type":"text","text":"输入输出重定向"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"一般情况下，每个 Unix/Linux 命令运行时都会打开三个文件："}]},{"type":"bulletedlist","content":[{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"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。"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"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。"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"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。"}]}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"默认情况下，command > file 将 stdout 重定向到 file，command < file 将stdin 重定向到 file。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"如果希望执行某个命令，但又不希望在屏幕上显示输出结果，那么可以将输出重定向到 /dev/null："}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong"}],"text":"输入重定向"}]},{"type":"numberedlist","attrs":{"start":"1","normalizeStart":1},"content":[{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":1,"align":null,"origin":null},"content":[{"type":"text","text":"bash.sh < file ： 将脚本的输入重定向到file，由file提供参数"}]}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong"}],"text":"输出重定向"}]},{"type":"numberedlist","attrs":{"start":"1","normalizeStart":1},"content":[{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":1,"align":null,"origin":null},"content":[{"type":"text","text":"bash.sh > file ： 将脚本的输出数据重定向到file中，覆盖数据"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":2,"align":null,"origin":null},"content":[{"type":"text","text":"bash.sh >> file ： 将脚本的输出数据重定向到file中，追加数据"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":3,"align":null,"origin":null},"content":[{"type":"text","text":" command >> file 2>&1 ： 将 stdout 和 stderr 合并后重定向到 file"}]}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"heading","attrs":{"align":null,"level":4},"content":[{"type":"text","text":"读取外部输入"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"命令："},{"type":"codeinline","content":[{"type":"text","text":"read arg"}]},{"type":"text","text":" （脚本读取外部输入并赋值到变量上）"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"在shell脚本执行到上述命令时，停止脚本执行并等待外部输入，将外部输入赋值到arg变量上，继续执行脚本"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"heading","attrs":{"align":null,"level":4},"content":[{"type":"text","text":"文件引用"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"引用其他的文件之后，可以使用其变量、函数等等，相当于将引用的文件包含进了当前文件"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"两种方式："}]},{"type":"numberedlist","attrs":{"start":"1","normalizeStart":1},"content":[{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":1,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong"}],"text":"."},{"type":"text","text":" file"},{"type":"text","marks":[{"type":"italic"}],"text":"path\\file"},{"type":"text","text":"name"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":2,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong"}],"text":"source"},{"type":"text","text":" file"},{"type":"text","marks":[{"type":"italic"}],"text":"path\\file"},{"type":"text","text":"name"}]}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"heading","attrs":{"align":null,"level":4},"content":[{"type":"text","text":"颜色标识"}]},{"type":"codeblock","attrs":{"lang":"shell"},"content":[{"type":"text","text":"printf \"\\033[32m SUCCESS: yay \\033[0m\\n\";\nprintf \"\\033[33m WARNING: hmm \\033[0m\\n\";\nprintf \"\\033[31m ERROR: fubar \\033[0m\\n\";"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"输出结果："}]},{"type":"image","attrs":{"src":"https://static001.geekbang.org/infoq/72/72bea1512f1619bd0736376e2dc256eb.png","alt":"在这里插入图片描述","title":null,"style":null,"href":null,"fromPaste":true,"pastePass":true}},{"type":"heading","attrs":{"align":null,"level":4},"content":[{"type":"text","text":"长句换行"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"在shell中为避免一个语句过长，可以使用“\\”进行换行"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"使用“\\”换行，在脚本执行过程中还是当做一行一个语句执行，不同于enter直接换行"}]},{"type":"blockquote","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"注意：\\ 前添加一个空格 。 \\ 后无空格直接换行。"}]}]},{"type":"codeblock","attrs":{"lang":"shell"},"content":[{"type":"text","text":" /mysql/bin/mysql \\\n -h test_host -P 000 \\\n -u test_user -ptest_password ;"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"heading","attrs":{"align":null,"level":4},"content":[{"type":"text","text":"shell操作mysql"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"下面案例为登录mysql，并选择操作数据库，之后进行导入数据"}]},{"type":"codeblock","attrs":{"lang":"shell"},"content":[{"type":"text","text":" /mysql/mysql/bin/mysql \\\n -h test_host -P 000 \\\n -u test_user -ptest_password \\\n -e\"use test_database; source data_faile; \" # -e 代表执行sql语句"}]},{"type":"blockquote","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":" -u 用户名 "}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":" -p 用户密码 "}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":" -h 服务器ip地址 "}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":" -D 连接的数据库"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":" -N 不输出列信息 "}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":" -B 使用tab键 代替 分隔符 "}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":" -e 执行的SQL语句"}]}]},{"type":"heading","attrs":{"align":null,"level":4},"content":[{"type":"text","text":"退出脚本"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"命令："},{"type":"codeinline","content":[{"type":"text","text":"exit"}]},{"type":"text","text":" "}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"在退出脚本时使用不同的错误码，这样可以根据错误码来判断发生了什么错误。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":">在绝大多数 shell 脚本中，exit 0 表示执行成功，exit 1 表示发生错误。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"对错误与错误码进行一对一的映射，这样有助于脚本调试。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"命令："},{"type":"codeinline","content":[{"type":"text","text":"set -e 或者 set +e"}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"set -e表示从当前位置开始，如果出现任何错误都将触发exit。相反，set +e表示不管出现任何错误继续执行脚本。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":">如果脚本是有状态的（每个后续步骤都依赖前一个步骤），那么请使用set -e，在脚本出现错误时立即退出脚本。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"如果要求所有命令都要执行完（很少会这样），那么就使用set +e。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"heading","attrs":{"align":null,"level":4},"content":[{"type":"text","text":"shell脚本调试"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"检查是否有语法错误"},{"type":"codeinline","content":[{"type":"text","text":"-n"}]},{"type":"text","text":"："}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"codeinline","content":[{"type":"text","text":"bash -n script_name.sh"}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"使用下面的命令来执行并调试 Shell 脚本"},{"type":"codeinline","content":[{"type":"text","text":"-x"}]},{"type":"text","text":"："}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"codeinline","content":[{"type":"text","text":"bash -x script_name.sh"}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong"}],"text":"调试count_odd_number.sh 程序案例："}]},{"type":"codeblock","attrs":{"lang":"shell"},"content":[{"type":"text","text":"#!/usr/bin.env bash\n\n# 用于计算数组中奇数的和\n# @author liyangyang\n# @time 2019/09/17\n\nsum=0\nfor num in 1 2 3 4;do\n re=${num}%2\n if (( ${re} == 1 ));then\n sum=$[${sum}+${num}]\n fi\ndone\necho ${sum}"}]},{"type":"numberedlist","attrs":{"start":"1","normalizeStart":1},"content":[{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":1,"align":null,"origin":null},"content":[{"type":"text","text":"首先检查有无语法错误："}]}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"codeinline","content":[{"type":"text","text":"bash -n count_odd_number.sh"}]}]},{"type":"numberedlist","attrs":{"start":"2","normalizeStart":"2"},"content":[{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":2,"align":null,"origin":null},"content":[{"type":"text","text":"没有输出，说明没有错误，开始实际调试："}]}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"codeinline","content":[{"type":"text","text":"bash -x count_odd_number.sh"}]}]},{"type":"numberedlist","attrs":{"start":"3","normalizeStart":"3"},"content":[{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":3,"align":null,"origin":null},"content":[{"type":"text","text":"调试结果如下："}]}]}]},{"type":"codeblock","attrs":{"lang":"shell"},"content":[{"type":"text","text":"+ sum=0\n+ for num in 1 2 3 4\n+ re=1%2\n+ (( 1%2 == 1 ))\n+ sum=1\n+ for num in 1 2 3 4\n+ re=2%2\n+ (( 2%2 == 1 ))\n+ for num in 1 2 3 4\n+ re=3%2\n+ (( 3%2 == 1 ))\n+ sum=4\n+ for num in 1 2 3 4\n+ re=4%2\n+ (( 4%2 == 1 ))\n+ echo 4\n4"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"其中的输出显示了程序执行的每一步，通过观察程序执行的步骤是否满足预期从而达到调试的效果"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"带有 + 表示的是 Shell 调试器的输出，不带 + 表示程序的输出。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"heading","attrs":{"align":null,"level":4},"content":[{"type":"text","text":"案例："}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"这是es（ElasticSearch）官方启动服务的脚本，看可不可以理解吧~"}]},{"type":"codeblock","attrs":{"lang":"shell"},"content":[{"type":"text","text":"#!/usr/bin/env bash\n\n# CONTROLLING STARTUP:\n#\n# This script relies on a few environment variables to determine startup\n# behavior, those variables are:\n#\n# ES_PATH_CONF -- Path to config directory\n# ES_JAVA_OPTS -- External Java Opts on top of the defaults set\n#\n# Optionally, exact memory values can be set using the `ES_JAVA_OPTS`. Note that\n# the Xms and Xmx lines in the JVM options file must be commented out. Example\n# values are \"512m\", and \"10g\".\n#\n# ES_JAVA_OPTS=\"-Xms8g -Xmx8g\" ./bin/elasticsearch\n\nsource \"`dirname \"$0\"`\"/elasticsearch-env\n\nparse_jvm_options() {\n if [ -f \"$1\" ]; then\n echo \"`grep \"^-\" \"$1\" | tr '\\n' ' '`\"\n fi\n}\n\nES_JVM_OPTIONS=\"$ES_PATH_CONF\"/jvm.options\n\nES_JAVA_OPTS=\"`parse_jvm_options \"$ES_JVM_OPTIONS\"` $ES_JAVA_OPTS\"\n\n# manual parsing to find out, if process should be detached\nif ! echo $* | grep -E '(^-d |-d$| -d |--daemonize$|--daemonize )' > /dev/null; then\n exec \\\n \"$JAVA\" \\\n $ES_JAVA_OPTS \\\n -Des.path.home=\"$ES_HOME\" \\\n -Des.path.conf=\"$ES_PATH_CONF\" \\\n -cp \"$ES_CLASSPATH\" \\\n org.elasticsearch.bootstrap.Elasticsearch \\\n \"$@\"\nelse\n exec \\\n \"$JAVA\" \\\n $ES_JAVA_OPTS \\\n -Des.path.home=\"$ES_HOME\" \\\n -Des.path.conf=\"$ES_PATH_CONF\" \\\n -cp \"$ES_CLASSPATH\" \\\n org.elasticsearch.bootstrap.Elasticsearch \\\n \"$@\" \\\n /dev/null ; then\n exit 1\n fi\n exit 0\nfi\n\nexit $?"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong"}],"text":"推荐阅读："}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"link","attrs":{"href":"https://liyangyang.blog.csdn.net/article/details/100939749","title":""},"content":[{"type":"text","text":"Git-【技术干货】工作中Git的使用实践"}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"link","attrs":{"href":"https://liyangyang.blog.csdn.net/article/details/101035399","title":""},"content":[{"type":"text","text":"Git - 使用git不知道内部实现机制怎么行"}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"blockquote","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong"}],"text":"如果感觉这篇文章对您有所帮助，请点击一下“喜欢”或者“关注”博主，您的喜欢和关注将是我前进的最大动力！谢谢大家~"}]}]}]}