终端

引言

无论你是DevOps/SysOps工程师、开发人员，还是仅仅对Linux感兴趣的人，你都可以使用Bash脚本来组合不同的Linux命令并自动化无聊和重复的日常任务，从而让你专注于更高效和有趣的事情。

在这里你可以找到完成的Bash脚本速查表

Bash脚本头部（Shebang）

选项 1：

#!/bin/bash

​

选项 2：

#!/usr/bin/env bash

​

变量

#!/bin/bash
name="DevDojo"
echo "Hi there $name"

​

用户输入

#!/bin/bash

echo "What is your name?"
read name

echo "Hi there $name"
echo "Welcome to DevDojo!"

​

注释

要在Bash中添加注释，你需要在行首加上#符号。注释永远不会显示在屏幕上。

# This is a comment and will not be rendered on the screen

​

参数

#!/bin/bash

echo "Argument one is $1"
echo "Argument two is $2"
echo "Argument three is $3"

​

然后运行文件并传递三个参数：

bash ./arguments.sh dog cat bird

​

数组

my_array=("value 1" "value 2" "value 3" "value 4")

# Access a single element, this would output: value 2
echo ${my_array[1]}

# This would return the last element: value 4
echo ${my_array[-1]}

# This would output the total number of elements in the array, in our case, it is 4:
echo "${#my_array[@]}"

# This would output all of the elements of the array:
printf '%s\n' "${my_array[@]}"

​

条件表达式

文件表达式

## True if file exists.
[[ -a ${file} ]]

## True if file exists and is a block special file.
[[ -b ${file} ]]

## True if file exists and is a character special file.
[[ -c ${file} ]]

## True if file exists and is a directory.
[[ -d ${file} ]]

## True if file exists.
[[ -e ${file} ]]

## True if file exists and is a regular file.
[[ -f ${file} ]]

## True if file exists and is a symbolic link.
[[ -h ${file} ]]

## True if file exists and is readable.
[[ -r ${file} ]]

## True if file exists and has a size greater than zero.
[[ -s ${file} ]]

## True if file exists and is writable.
[[ -w ${file} ]]

## True if file exists and is executable.
[[ -x ${file} ]]

## True if file exists and is a symbolic link.
[[ -L ${file} ]]

​

字符串表达式

# True if the shell variable varname is set (has been assigned a value).
[[ -v ${varname} ]]

# True if the length of the string is zero.
[[ -z ${string} ]]

# True if the length of the string is non-zero.
[[ -n ${string} ]]

# True if the strings are equal. = should be used with the test command for POSIX conformance. When used with the [[ command, this performs pattern matching as described above (Compound Commands)
[[ ${string1} == ${string2} ]]

# True if the strings are not equal.
[[ ${string1} != ${string2} ]]

# True if string1 sorts before string2 lexicographically.
[[ ${string1} < ${string2} ]]

# True if string1 sorts after string2 lexicographically.
[[ ${string1} > ${string2} ]]

​

算术运算符

# Returns true if the numbers are equal
[[ ${arg1} -eq ${arg2} ]]

# Returns true if the numbers are not equal
[[ ${arg1} -ne ${arg2} ]]

# Returns true if arg1 is less than arg2
[[ ${arg1} -lt ${arg2} ]]

# Returns true if arg1 is less than or equal arg2
[[ ${arg1} -le ${arg2} ]]

# Returns true if arg1 is greater than arg2
[[ ${arg1} -gt ${arg2} ]]

# Returns true if arg1 is greater than or equal arg2
[[ ${arg1} -ge ${arg2} ]]

# As with other programming languages you can use AND & OR conditions:
[[ test_case_1 ]] && [[ test_case_2 ]] # And
[[ test_case_1 ]] || [[ test_case_2 ]] # Or

​

条件语句

#!/bin/bash

# Bash if statement example

read -p "What is your name? " name

if [[ -z ${name} ]]
then
    echo "Please enter your name!"
else
    echo "Hi there ${name}"
fi

​

循环

For循环

#!/bin/bash

users="devdojo, bobby, tony"

for user in ${users}
do
    echo "${user}"
done

​

While循环

#!/bin/bash

counter=1
while [[ $counter -le 10 ]]
do
    echo $counter
    ((counter++))
done

​

Until循环

#!/bin/bash

count=1
until [ $count -gt 10 ]
do
    echo $count
    ((count++))
done

​

函数

function function_name() {
    your_commands
}

​

示例

#!/bin/bash

function hello(){
    echo "Hello World Function!"
}

hello
​

声明:
本文件灏天文库团队进行了翻译。尽管我们力求准确，但请注意，翻译可能包含错误或不准确之处。原文档以其原始语言为准。我们不对因使用此翻译而产生的任何误解或误译负责。