967 lines
16 KiB
Markdown
967 lines
16 KiB
Markdown
Bash 备忘清单
|
||
===
|
||
|
||
这是开始使用 linux bash shell 脚本的快速参考备忘单。
|
||
|
||
入门
|
||
---------------
|
||
|
||
### hello.sh
|
||
|
||
```bash
|
||
#!/bin/bash
|
||
VAR="world"
|
||
echo "Hello $VAR!" # => Hello world!
|
||
```
|
||
|
||
执行脚本
|
||
|
||
```shell
|
||
$ bash hello.sh
|
||
```
|
||
|
||
### 变量
|
||
|
||
```bash
|
||
NAME="John"
|
||
echo ${NAME} # => John (变量)
|
||
echo $NAME # => John (变量)
|
||
echo "$NAME" # => John (变量)
|
||
echo '$NAME' # => $NAME (字符串原样输出)
|
||
echo "${NAME}!" # => John! (变量)
|
||
NAME = "John" # => Error (注意不能有空格)
|
||
```
|
||
|
||
### 注释
|
||
|
||
```shell
|
||
# 这是一个内联 Bash 注释。
|
||
|
||
: '
|
||
这是一个
|
||
非常整洁的
|
||
bash 注释
|
||
'
|
||
```
|
||
|
||
多行注释使用 `:'` 打开和 `'` 关闭
|
||
|
||
### 参数
|
||
<!--rehype:wrap-class=row-span-2-->
|
||
|
||
表示 | 描述
|
||
:-|-
|
||
`$1` … `$9` | 参数 1 ... 9
|
||
`$0` | 脚本本身的名称
|
||
`$1` | 第一个参数
|
||
`${10}` | 位置参数 10
|
||
`$#` | 参数数量
|
||
`$$` | shell 的进程 id
|
||
`$*` | 所有参数
|
||
`$@` | 所有参数，从第一个开始
|
||
`$-` | 当前选项
|
||
`$_` | 上一个命令的最后一个参数
|
||
|
||
见：[特殊参数](http://wiki.bash-hackers.org/syntax/shellvars#special_parameters_and_shell_variables)
|
||
|
||
### 函数
|
||
|
||
```bash
|
||
get_name() {
|
||
echo "John"
|
||
}
|
||
echo "You are $(get_name)"
|
||
```
|
||
|
||
见：[函数](#bash-函数)
|
||
|
||
### 条件句
|
||
|
||
```bash
|
||
if [[ -z "$string" ]]; then
|
||
echo "String is empty"
|
||
elif [[ -n "$string" ]]; then
|
||
echo "String is not empty"
|
||
fi
|
||
```
|
||
|
||
见：[条件句](#bash-条件句)
|
||
|
||
### 大括号扩展
|
||
|
||
```shell
|
||
echo {A,B}.js
|
||
```
|
||
|
||
---
|
||
|
||
表示 | 描述
|
||
:-|-
|
||
`{A,B}` | 与 `A B` 相同
|
||
`{A,B}.js` | 与 `A.js B.js` 相同
|
||
`{1..5}` | 与 `1 2 3 4 5` 相同
|
||
|
||
见：[大括号扩展](http://wiki.bash-hackers.org/syntax/expansion/brace)
|
||
|
||
### Shell 执行
|
||
|
||
```bash
|
||
# => I'm in /当前/的/路径
|
||
echo "I'm in $(PWD)"
|
||
# Same as:
|
||
echo "I'm in `pwd`"
|
||
```
|
||
|
||
见：[命令替换](http://wiki.bash-hackers.org/syntax/expansion/cmdsubst)
|
||
|
||
Bash 参数扩展
|
||
-----
|
||
|
||
### 语法
|
||
<!--rehype:wrap-class=row-span-2-->
|
||
|
||
代码 | 描述
|
||
:-|-
|
||
`${FOO%suffix}` | 删除后缀
|
||
`${FOO#prefix}` | 删除前缀
|
||
`${FOO%%suffix}` | 去掉长后缀
|
||
`${FOO##prefix}` | 删除长前缀
|
||
`${FOO/from/to}` | 替换第一个匹配项
|
||
`${FOO//from/to}` | 全部替换
|
||
`${FOO/%from/to}` | 替换后缀
|
||
`${FOO/#from/to}` | 替换前缀
|
||
|
||
#### 子字符串
|
||
|
||
表示 | 描述
|
||
:-|-
|
||
`${FOO:0:3}` | 子串 _(位置，长度)_
|
||
`${FOO:(-3):3}` | 从右边开始的子串
|
||
|
||
#### Length
|
||
|
||
表示 | 描述
|
||
:-|-
|
||
`${#FOO}` | `$FOO` 的长度
|
||
|
||
#### 默认值
|
||
|
||
表示 | 描述
|
||
:-|-
|
||
`${FOO:-val}` | `$FOO`，如果未设置，则为 `val`
|
||
`${FOO:=val}` | 如果未设置，则将 `$FOO` 设置为 `val`
|
||
`${FOO:+val}` | `val` 如果设置了`$FOO`
|
||
`${FOO:?message}` | 如果 `$FOO` 未设置，则显示消息并退出
|
||
|
||
### 替代 Substitution
|
||
|
||
```bash
|
||
echo ${food:-Cake} #=> $food or "Cake"
|
||
```
|
||
|
||
```bash
|
||
STR="/path/to/foo.cpp"
|
||
echo ${STR%.cpp} # /path/to/foo
|
||
echo ${STR%.cpp}.o # /path/to/foo.o
|
||
echo ${STR%/*} # /path/to
|
||
echo ${STR##*.} # cpp (extension)
|
||
echo ${STR##*/} # foo.cpp (basepath)
|
||
echo ${STR#*/} # path/to/foo.cpp
|
||
echo ${STR##*/} # foo.cpp
|
||
echo ${STR/foo/bar} # /path/to/bar.cpp
|
||
```
|
||
|
||
### 切片 Slicing
|
||
|
||
```bash
|
||
name="John"
|
||
echo ${name} # => John
|
||
echo ${name:0:2} # => Jo
|
||
echo ${name::2} # => Jo
|
||
echo ${name::-1} # => Joh
|
||
echo ${name:(-1)} # => n
|
||
echo ${name:(-2)} # => hn
|
||
echo ${name:(-2):2} # => hn
|
||
|
||
length=2
|
||
echo ${name:0:length} # => Jo
|
||
```
|
||
|
||
见：[参数扩展](http://wiki.bash-hackers.org/syntax/pe)
|
||
|
||
### 基本路径和目录路径
|
||
|
||
```bash
|
||
SRC="/path/to/foo.cpp"
|
||
```
|
||
|
||
```bash
|
||
BASEPATH=${SRC##*/}
|
||
echo $BASEPATH # => "foo.cpp"
|
||
|
||
DIRPATH=${SRC%$BASEPATH}
|
||
echo $DIRPATH # => "/path/to/"
|
||
```
|
||
|
||
### Transform
|
||
|
||
```bash
|
||
STR="HELLO WORLD!"
|
||
echo ${STR,} # => hELLO WORLD!
|
||
echo ${STR,,} # => hello world!
|
||
|
||
STR="hello world!"
|
||
echo ${STR^} # => Hello world!
|
||
echo ${STR^^} # => HELLO WORLD!
|
||
|
||
ARR=(hello World)
|
||
echo "${ARR[@],}" # => hello world
|
||
echo "${ARR[@]^}" # => Hello World
|
||
```
|
||
|
||
Bash 数组
|
||
------
|
||
|
||
### 定义数组
|
||
|
||
```bash
|
||
Fruits=('Apple' 'Banana' 'Orange')
|
||
|
||
Fruits[0]="Apple"
|
||
Fruits[1]="Banana"
|
||
Fruits[2]="Orange"
|
||
|
||
ARRAY1=(foo{1..2}) # => foo1 foo2
|
||
ARRAY2=({A..D}) # => A B C D
|
||
|
||
# 合并 => foo1 foo2 A B C D
|
||
ARRAY3=(${ARRAY1[@]} ${ARRAY2[@]})
|
||
|
||
# 声明构造
|
||
declare -a Numbers=(1 2 3)
|
||
Numbers+=(4 5) # 附加 => 1 2 3 4 5
|
||
```
|
||
|
||
### 索引
|
||
|
||
:- | -
|
||
:- | -
|
||
`${Fruits[0]}` | 第一个元素
|
||
`${Fruits[-1]}` | 最后一个元素
|
||
`${Fruits[*]}` | 所有元素
|
||
`${Fruits[@]}` | 所有元素
|
||
`${#Fruits[@]}` | 总数
|
||
`${#Fruits}` | 第一节长度
|
||
`${#Fruits[3]}` | 第n个长度
|
||
`${Fruits[@]:3:2}` | 范围
|
||
`${!Fruits[@]}` | 所有 Key
|
||
|
||
### 迭代 Iteration
|
||
|
||
```bash
|
||
Fruits=('Apple' 'Banana' 'Orange')
|
||
for e in "${Fruits[@]}"; do
|
||
echo $e
|
||
done
|
||
```
|
||
|
||
#### With index
|
||
|
||
```bash
|
||
for i in "${!Fruits[@]}"; do
|
||
printf "%s\t%s\n" "$i" "${Fruits[$i]}"
|
||
done
|
||
```
|
||
|
||
### 操作
|
||
<!--rehype:wrap-class=col-span-2-->
|
||
|
||
```bash
|
||
Fruits=("${Fruits[@]}" "Watermelon") # 添加
|
||
Fruits+=('Watermelon') # 也是添加
|
||
Fruits=( ${Fruits[@]/Ap*/} ) # 通过正则表达式匹配删除
|
||
unset Fruits[2] # 删除一项
|
||
Fruits=("${Fruits[@]}") # 复制
|
||
Fruits=("${Fruits[@]}" "${Veggies[@]}") # 连接
|
||
lines=(`cat "logfile"`) # 从文件中读取
|
||
```
|
||
|
||
### 数组作为参数
|
||
|
||
```bash
|
||
function extract()
|
||
{
|
||
local -n myarray=$1
|
||
local idx=$2
|
||
echo "${myarray[$idx]}"
|
||
}
|
||
Fruits=('Apple' 'Banana' 'Orange')
|
||
extract Fruits 2 # => Orangle
|
||
```
|
||
|
||
Bash 字典
|
||
------------
|
||
|
||
### 定义
|
||
|
||
```bash
|
||
declare -A sounds
|
||
```
|
||
|
||
```bash
|
||
sounds[dog]="bark"
|
||
sounds[cow]="moo"
|
||
sounds[bird]="tweet"
|
||
sounds[wolf]="howl"
|
||
```
|
||
|
||
### 使用字典
|
||
|
||
```bash
|
||
echo ${sounds[dog]} # Dog's sound
|
||
echo ${sounds[@]} # All values
|
||
echo ${!sounds[@]} # All keys
|
||
echo ${#sounds[@]} # Number of elements
|
||
unset sounds[dog] # Delete dog
|
||
```
|
||
|
||
### 迭代
|
||
|
||
```bash
|
||
for val in "${sounds[@]}"; do
|
||
echo $val
|
||
done
|
||
```
|
||
|
||
---
|
||
|
||
```bash
|
||
for key in "${!sounds[@]}"; do
|
||
echo $key
|
||
done
|
||
```
|
||
|
||
Bash 条件句
|
||
------------
|
||
|
||
### 整数条件
|
||
|
||
条件 | 描述
|
||
:- | -
|
||
`[[ NUM -eq NUM ]]` | 等于 <yel>Eq</yel>ual |
|
||
`[[ NUM -ne NUM ]]` | 不等于 <yel>N</yel>ot <yel>e</yel>qual |
|
||
`[[ NUM -lt NUM ]]` | 小于 <yel>L</yel>ess <yel>t</yel>han |
|
||
`[[ NUM -le NUM ]]` | 小于等于 <yel>L</yel>ess than or <yel>e</yel>qual |
|
||
`[[ NUM -gt NUM ]]` | 大于 <yel>G</yel>reater <yel>t</yel>han |
|
||
`[[ NUM -ge NUM ]]` | 大于等于 <yel>G</yel>reater than or <yel>e</yel>qual |
|
||
`(( NUM < NUM ))` | 小于
|
||
`(( NUM <= NUM ))` | 小于或等于
|
||
`(( NUM > NUM ))` | 比...更大
|
||
`(( NUM >= NUM ))` | 大于等于
|
||
|
||
### 字符串条件
|
||
|
||
条件 | 描述
|
||
:- | -
|
||
`[[ -z STR ]]` | 空字符串
|
||
`[[ -n STR ]]` | <yel>非</yel>空字符串
|
||
`[[ STR == STR ]]` | 相等
|
||
`[[ STR = STR ]]` | 相等（同上）
|
||
`[[ STR < STR ]]` | 小于 _(ASCII)_
|
||
`[[ STR > STR ]]` | 大于 _(ASCII)_
|
||
`[[ STR != STR ]]` | 不相等
|
||
`[[ STR =~ STR ]]` | 正则表达式
|
||
|
||
### 例子
|
||
<!--rehype:wrap-class=row-span-3-->
|
||
|
||
#### 字符串
|
||
|
||
```bash
|
||
if [[ -z "$string" ]]; then
|
||
echo "String is empty"
|
||
elif [[ -n "$string" ]]; then
|
||
echo "String is not empty"
|
||
else
|
||
echo "This never happens"
|
||
fi
|
||
```
|
||
|
||
#### 组合
|
||
|
||
```bash
|
||
if [[ X && Y ]]; then
|
||
...
|
||
fi
|
||
```
|
||
|
||
#### 相等
|
||
|
||
```bash
|
||
if [[ "$A" == "$B" ]]; then
|
||
...
|
||
fi
|
||
```
|
||
|
||
#### 正则表达式
|
||
|
||
```bash
|
||
if [[ '1. abc' =~ ([a-z]+) ]]; then
|
||
echo ${BASH_REMATCH[1]}
|
||
fi
|
||
```
|
||
|
||
#### 小于
|
||
|
||
```bash
|
||
if (( $a < $b )); then
|
||
echo "$a is smaller than $b"
|
||
fi
|
||
```
|
||
|
||
#### 存在
|
||
|
||
```bash
|
||
if [[ -e "file.txt" ]]; then
|
||
echo "file exists"
|
||
fi
|
||
```
|
||
|
||
### 文件条件
|
||
<!--rehype:wrap-class=row-span-2-->
|
||
|
||
条件 | 描述
|
||
:- | -
|
||
`[[ -e FILE ]]` | 存在
|
||
`[[ -d FILE ]]` | 目录
|
||
`[[ -f FILE ]]` | 文件
|
||
`[[ -h FILE ]]` | 符号链接
|
||
`[[ -s FILE ]]` | 大小 > 0 字节
|
||
`[[ -r FILE ]]` | 可读
|
||
`[[ -w FILE ]]` | 可写
|
||
`[[ -x FILE ]]` | 可执行文件
|
||
`[[ f1 -nt f2 ]]` | f1 比 f2 新
|
||
`[[ f1 -ot f2 ]]` | f2 比 f1 新
|
||
`[[ f1 -ef f2 ]]` | 相同的文件
|
||
|
||
### 更多条件
|
||
|
||
条件 | 描述
|
||
:- | -
|
||
`[[ -o noclobber ]]` | 如果启用 OPTION
|
||
`[[ ! EXPR ]]` | 不是 Not
|
||
`[[ X && Y ]]` | 和 And
|
||
`[[ X \|\| Y ]]` | 或者 Or
|
||
|
||
### 逻辑和，或
|
||
|
||
```bash
|
||
if [ "$1" = 'y' -a $2 -gt 0 ]; then
|
||
echo "yes"
|
||
fi
|
||
if [ "$1" = 'n' -o $2 -lt 0 ]; then
|
||
echo "no"
|
||
fi
|
||
```
|
||
|
||
Bash 循环
|
||
-----
|
||
|
||
### 基本 for 循环
|
||
|
||
```bash
|
||
for i in /etc/rc.*; do
|
||
echo $i
|
||
done
|
||
```
|
||
|
||
### 类似 C 的 for 循环
|
||
|
||
```bash
|
||
for ((i = 0 ; i < 100 ; i++)); do
|
||
echo $i
|
||
done
|
||
```
|
||
|
||
### 范围
|
||
<!--rehype:wrap-class=row-span-2-->
|
||
|
||
```bash
|
||
for i in {1..5}; do
|
||
echo "Welcome $i"
|
||
done
|
||
```
|
||
|
||
#### 步长
|
||
|
||
```bash
|
||
for i in {5..50..5}; do
|
||
echo "Welcome $i"
|
||
done
|
||
```
|
||
|
||
### 自动递增
|
||
|
||
```bash
|
||
i=1
|
||
while [[ $i -lt 4 ]]; do
|
||
echo "Number: $i"
|
||
((i++))
|
||
done
|
||
```
|
||
|
||
### 自动递减
|
||
|
||
```bash
|
||
i=3
|
||
while [[ $i -gt 0 ]]; do
|
||
echo "Number: $i"
|
||
((i--))
|
||
done
|
||
```
|
||
|
||
### Continue
|
||
|
||
```bash {data=3,5}
|
||
for number in $(seq 1 3); do
|
||
if [[ $number == 2 ]]; then
|
||
continue;
|
||
fi
|
||
echo "$number"
|
||
done
|
||
```
|
||
|
||
### Break
|
||
|
||
```bash
|
||
for number in $(seq 1 3); do
|
||
if [[ $number == 2 ]]; then
|
||
# Skip entire rest of loop.
|
||
break;
|
||
fi
|
||
# This will only print 1
|
||
echo "$number"
|
||
done
|
||
```
|
||
|
||
### Until
|
||
|
||
```bash
|
||
count=0
|
||
until [ $count -gt 10 ]; do
|
||
echo "$count"
|
||
((count++))
|
||
done
|
||
```
|
||
|
||
### 死循环
|
||
|
||
```bash
|
||
while true; do
|
||
# here is some code.
|
||
done
|
||
```
|
||
|
||
### 死循环（简写）
|
||
|
||
```bash
|
||
while :; do
|
||
# here is some code.
|
||
done
|
||
```
|
||
|
||
### 读取文件的每一行
|
||
|
||
```bash
|
||
cat file.txt | while read line; do
|
||
echo $line
|
||
done
|
||
```
|
||
|
||
Bash 函数
|
||
---------
|
||
|
||
### 定义函数
|
||
|
||
```bash
|
||
myfunc() {
|
||
echo "hello $1"
|
||
}
|
||
```
|
||
|
||
```bash
|
||
# 同上（替代语法）
|
||
function myfunc() {
|
||
echo "hello $1"
|
||
}
|
||
```
|
||
|
||
```bash
|
||
myfunc "John"
|
||
```
|
||
|
||
### 返回值
|
||
|
||
```bash
|
||
myfunc() {
|
||
local myresult='some value'
|
||
echo $myresult
|
||
}
|
||
```
|
||
|
||
```bash
|
||
result="$(myfunc)"
|
||
```
|
||
|
||
### 抛出错误
|
||
|
||
```bash
|
||
myfunc() {
|
||
return 1
|
||
}
|
||
```
|
||
|
||
```bash
|
||
if myfunc; then
|
||
echo "success"
|
||
else
|
||
echo "failure"
|
||
fi
|
||
```
|
||
|
||
Bash 选项
|
||
-------
|
||
<!--rehype:body-class=cols-2-->
|
||
|
||
### 选项
|
||
|
||
```bash
|
||
# 避免覆盖文件
|
||
# (echo "hi" > foo)
|
||
set -o noclobber
|
||
|
||
# 用于出错时退出
|
||
# 避免级联错误
|
||
set -o errexit
|
||
|
||
# 揭示隐藏的失败
|
||
set -o pipefail
|
||
|
||
# 公开未设置的变量
|
||
set -o nounset
|
||
```
|
||
|
||
### 全局选项
|
||
|
||
```bash
|
||
# 不匹配的 glob 被删除
|
||
# ('*.foo' => '')
|
||
shopt -s nullglob
|
||
|
||
# 不匹配的 glob 抛出错误
|
||
shopt -s failglob
|
||
|
||
# 不区分大小写的球体
|
||
shopt -s nocaseglob
|
||
|
||
# 通配符匹配点文件
|
||
# ("*.sh" => ".foo.sh")
|
||
shopt -s dotglob
|
||
|
||
# 允许 ** 进行递归匹配
|
||
# ('lib/**/*.rb' => 'lib/a/b/c.rb')
|
||
shopt -s globstar
|
||
```
|
||
|
||
Bash 历史
|
||
-------
|
||
<!--rehype:body-class=cols-2-->
|
||
|
||
### 命令
|
||
|
||
命令 | 描述
|
||
:- | -
|
||
`history` | 显示历史
|
||
`sudo !!` | 使用 sudo 运行上一个命令
|
||
`shopt -s histverify` | 不要立即执行扩展结果
|
||
|
||
### 表达式
|
||
|
||
表达式 | 描述
|
||
:- | -
|
||
`!$` | 展开最新命令的最后一个参数
|
||
`!*` | 展开最新命令的所有参数
|
||
`!-n` | 展开第 `n` 个最近的命令
|
||
`!n` | 展开历史中的第 `n` 个命令
|
||
`!<command>` | 展开最近调用的命令 `<command>`
|
||
|
||
### 操作
|
||
|
||
代码 | 描述
|
||
:- | -
|
||
`!!` | 再次执行最后一条命令
|
||
`!!:s/<FROM>/<TO>/` | 在最近的命令中将第一次出现的 `<FROM>` 替换为 `<TO>`
|
||
`!!:gs/<FROM>/<TO>/` | 在最近的命令中将所有出现的 `<FROM>` 替换为 `<TO>`
|
||
`!$:t` | 仅从最近命令的最后一个参数扩展基本名称
|
||
`!$:h` | 仅从最近命令的最后一个参数展开目录
|
||
|
||
`!!` 和 `!$` 可以替换为任何有效的扩展。
|
||
|
||
### 切片 Slices
|
||
|
||
代码 | 描述
|
||
:- | -
|
||
`!!:n` | 仅扩展最近命令中的第 `n` 个标记（命令为 `0`；第一个参数为 `1`）
|
||
`!^` | 从最近的命令展开第一个参数
|
||
`!$` | 从最近的命令中展开最后一个标记
|
||
`!!:n-m` | 从最近的命令扩展令牌范围
|
||
`!!:n-$` | 从最近的命令中将第 `n` 个标记展开到最后
|
||
|
||
`!!` 可以替换为任何有效的扩展，即 `!cat`、`!-2`、`!42` 等。
|
||
|
||
杂项
|
||
-------------
|
||
|
||
### 数值计算
|
||
|
||
```bash
|
||
$((a + 200)) # Add 200 to $a
|
||
```
|
||
|
||
```bash
|
||
$(($RANDOM%200)) # Random number 0..199
|
||
```
|
||
|
||
### 子 shell
|
||
|
||
```bash
|
||
(cd somedir; echo "I'm now in $PWD")
|
||
pwd # still in first directory
|
||
```
|
||
|
||
### 检查命令
|
||
|
||
```bash
|
||
command -V cd
|
||
#=> "cd is a function/alias/whatever"
|
||
```
|
||
|
||
### 重定向
|
||
<!--rehype:wrap-class=row-span-2 col-span-2-->
|
||
|
||
```bash
|
||
python hello.py > output.txt # 标准输出到（文件）
|
||
python hello.py >> output.txt # 标准输出到（文件），追加
|
||
python hello.py 2> error.log # 标准错误到（文件）
|
||
python hello.py 2>&1 # 标准错误到标准输出
|
||
python hello.py 2>/dev/null # 标准错误到（空null）
|
||
python hello.py &>/dev/null # 标准输出和标准错误到（空null）
|
||
```
|
||
|
||
```bash
|
||
python hello.py < foo.txt # 将 foo.txt 提供给 python 的标准输入
|
||
```
|
||
|
||
### 来源相对
|
||
|
||
```bash
|
||
source "${0%/*}/../share/foo.sh"
|
||
```
|
||
|
||
### 脚本目录
|
||
|
||
```bash
|
||
DIR="${0%/*}"
|
||
```
|
||
|
||
### Case/switch
|
||
|
||
```bash
|
||
case "$1" in
|
||
start | up)
|
||
vagrant up
|
||
;;
|
||
*)
|
||
echo "Usage: $0 {start|stop|ssh}"
|
||
;;
|
||
esac
|
||
```
|
||
|
||
### 陷阱错误
|
||
<!--rehype:wrap-class=col-span-2-->
|
||
|
||
```bash
|
||
trap 'echo Error at about $LINENO' ERR
|
||
```
|
||
|
||
或者
|
||
|
||
```bash
|
||
traperr() {
|
||
echo "ERROR: ${BASH_SOURCE[1]} at about ${BASH_LINENO[0]}"
|
||
}
|
||
set -o errtrace
|
||
trap traperr ERR
|
||
```
|
||
|
||
### printf
|
||
|
||
```bash
|
||
printf "Hello %s, I'm %s" Sven Olga
|
||
#=> "Hello Sven, I'm Olga
|
||
|
||
printf "1 + 1 = %d" 2
|
||
#=> "1 + 1 = 2"
|
||
|
||
printf "Print a float: %f" 2
|
||
#=> "Print a float: 2.000000"
|
||
```
|
||
|
||
### 获取选项
|
||
<!--rehype:wrap-class=col-span-2-->
|
||
|
||
```bash
|
||
while [[ "$1" =~ ^- && ! "$1" == "--" ]]; do case $1 in
|
||
-V | --version )
|
||
echo $version
|
||
exit
|
||
;;
|
||
-s | --string )
|
||
shift; string=$1
|
||
;;
|
||
-f | --flag )
|
||
flag=1
|
||
;;
|
||
esac; shift; done
|
||
if [[ "$1" == '--' ]]; then shift; fi
|
||
```
|
||
|
||
### 检查命令的结果
|
||
<!--rehype:wrap-class=col-span-2-->
|
||
|
||
```bash
|
||
if ping -c 1 google.com; then
|
||
echo "看来您的互联网连接正常"
|
||
fi
|
||
```
|
||
|
||
### 特殊变量
|
||
<!--rehype:wrap-class=row-span-2-->
|
||
|
||
表达式 | 描述
|
||
:- | -
|
||
`$?` | 最后一个任务的退出状态
|
||
`$!` | 最后一个后台任务的 PID
|
||
`$$` | shell PID
|
||
`$0` | shell 脚本的文件名
|
||
|
||
见[特殊参数](http://wiki.bash-hackers.org/syntax/shellvars#special_parameters_and_shell_variables)。
|
||
|
||
### grep 检查
|
||
<!--rehype:wrap-class=col-span-2-->
|
||
|
||
```bash
|
||
if grep -q 'foo' ~/.bash_history; then
|
||
echo "您过去似乎输入过“foo”"
|
||
fi
|
||
```
|
||
|
||
### 反斜杠转义
|
||
<!--rehype:wrap-class=row-span-2-->
|
||
|
||
-
|
||
- \!
|
||
- \"
|
||
- \#
|
||
- \&
|
||
- \'
|
||
- \(
|
||
- \)
|
||
- \,
|
||
- \;
|
||
- \<
|
||
- \>
|
||
- \[
|
||
- \|
|
||
- \\
|
||
- \]
|
||
- \^
|
||
- \{
|
||
- \}
|
||
- \`
|
||
- \$
|
||
- \*
|
||
- \?
|
||
<!--rehype:className=cols-4 style-none-->
|
||
|
||
使用 `\` 转义这些特殊字符
|
||
|
||
### Heredoc
|
||
|
||
```sh
|
||
cat <<END
|
||
hello world
|
||
END
|
||
```
|
||
|
||
### 转到上一个目录
|
||
|
||
```bash
|
||
pwd # /home/user/foo
|
||
cd bar/
|
||
pwd # /home/user/foo/bar
|
||
cd -
|
||
pwd # /home/user/foo
|
||
```
|
||
|
||
### 读取输入
|
||
|
||
```bash
|
||
echo -n "Proceed? [y/n]: "
|
||
read ans
|
||
echo $ans
|
||
```
|
||
|
||
```bash
|
||
read -n 1 ans # 只有一个字符
|
||
```
|
||
|
||
### 条件执行
|
||
|
||
```bash
|
||
git commit && git push
|
||
git commit || echo "Commit failed"
|
||
```
|
||
|
||
### 严格模式
|
||
|
||
```bash
|
||
set -euo pipefail
|
||
IFS=$'\n\t'
|
||
```
|
||
|
||
参见：[非官方 bash 严格模式](http://redsymbol.net/articles/unofficial-bash-strict-mode/)
|
||
|
||
### 可选参数
|
||
|
||
```bash
|
||
args=("$@")
|
||
args+=(foo)
|
||
args+=(bar)
|
||
echo "${args[@]}"
|
||
```
|
||
|
||
将参数放入数组中，然后追加
|
||
|
||
另见
|
||
----
|
||
|
||
- [Shell 教程](https://jaywcjlove.github.io/shell-tutorial) _(jaywcjlove.github.io)_
|
||
- [Devhints](https://devhints.io/bash) _(devhints.io)_
|
||
- [Bash-hackers wiki](http://wiki.bash-hackers.org/) _(bash-hackers.org)_
|
||
- [Shell vars](http://wiki.bash-hackers.org/syntax/shellvars) _(bash-hackers.org)_
|
||
- [Learn bash in y minutes](https://learnxinyminutes.com/docs/bash/) _(learnxinyminutes.com)_
|
||
- [Bash Guide](http://mywiki.wooledge.org/BashGuide) _(mywiki.wooledge.org)_
|
||
- [ShellCheck](https://www.shellcheck.net/) _(shellcheck.net)_
|
||
- [shell - Standard Shell](https://devmanual.gentoo.org/tools-reference/bash/index.html) _(devmanual.gentoo.org)_
|