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Merge pull request #1102 from Alwayswithme/bash-cn
[bash/cn]update bash-cn
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@ -5,7 +5,14 @@ contributors:
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- ["Max Yankov", "https://github.com/golergka"]
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- ["Darren Lin", "https://github.com/CogBear"]
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- ["Alexandre Medeiros", "http://alemedeiros.sdf.org"]
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- ["Denis Arh", "https://github.com/darh"]
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- ["akirahirose", "https://twitter.com/akirahirose"]
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- ["Anton Strömkvist", "http://lutic.org/"]
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- ["Rahil Momin", "https://github.com/iamrahil"]
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- ["Gregrory Kielian", "https://github.com/gskielian"]
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- ["Etan Reisner", "https://github.com/deryni"]
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translators:
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- ["Jinchang Ye", "https://github.com/Alwayswithme"]
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- ["Chunyang Xu", "https://github.com/XuChunyang"]
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filename: LearnBash-cn.sh
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lang: zh-cn
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@ -23,31 +30,45 @@ Bash 是一个为 GNU 计划编写的 Unix shell,是 Linux 和 Mac OS X 下的
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# 如你所见,注释以 # 开头,shebang 也是注释。
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# 显示 “Hello world!”
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echo Hello, world!
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echo Hello world!
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# 每一句指令以换行或分号隔开:
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echo 'This is the first line'; echo 'This is the second line'
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# 声明一个变量:
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VARIABLE="Some string"
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Variable="Some string"
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# 下面是错误的做法:
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VARIABLE = "Some string"
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# Bash 会把 VARIABLE 当做一个指令,由于找不到该指令,因此这里会报错。
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Variable = "Some string"
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# Bash 会把 Variable 当做一个指令,由于找不到该指令,因此这里会报错。
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# 也不可以这样:
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Variable= 'Some string'
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# Bash 会认为 'Some string' 是一条指令,由于找不到该指令,这里再次报错。
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# (这个例子中 'Variable=' 这部分会被当作仅对 'Some string' 起作用的赋值。)
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# 使用变量:
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echo $VARIABLE
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echo "$VARIABLE"
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echo '$VARIABLE'
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echo $Variable
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echo "$Variable"
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echo '$Variable'
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# 当你赋值 (assign) 、导出 (export),或者以其他方式使用变量时,变量名前不加 $。
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# 如果要使用变量的值, 则要加 $。
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# 注意: ' (单引号) 不会展开变量(即会屏蔽掉变量)。
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# 在变量内部进行字符串代换
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echo ${VARIABLE/Some/A}
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# 会把 VARIABLE 中首次出现的 "some" 替换成 “A”。
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echo ${Variable/Some/A}
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# 会把 Variable 中首次出现的 "some" 替换成 “A”。
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# 变量的截取
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Length=7
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echo ${Variable:0:Length}
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# 这样会仅返回变量值的前7个字符
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# 变量的默认值
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echo ${Foo:-"DefaultValueIfFooIsMissingOrEmpty"}
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# 对 null (Foo=) 和空串 (Foo="") 起作用; 零(Foo=0)时返回0
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# 注意这仅返回默认值而不是改变变量的值
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# 内置变量:
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# 下面的内置变量很有用
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@ -55,26 +76,37 @@ echo "Last program return value: $?"
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echo "Script's PID: $$"
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echo "Number of arguments: $#"
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echo "Scripts arguments: $@"
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echo "Scripts arguments separeted in different variables: $1 $2..."
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echo "Scripts arguments separated in different variables: $1 $2..."
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# 读取输入:
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echo "What's your name?"
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read NAME # 这里不需要声明新变量
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echo Hello, $NAME!
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read Name # 这里不需要声明新变量
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echo Hello, $Name!
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# 通常的 if 结构看起来像这样:
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# 'man test' 可查看更多的信息
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if [ $NAME -ne $USER ]
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if [ $Name -ne $USER ]
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then
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echo "Your name is you username"
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echo "Your name isn't your username"
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else
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echo "Your name isn't you username"
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echo "Your name is your username"
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fi
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# 根据上一个指令执行结果决定是否执行下一个指令
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echo "Always executed" || echo "Only executed if first command fail"
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echo "Always executed" || echo "Only executed if first command fails"
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echo "Always executed" && echo "Only executed if first command does NOT fail"
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# 在 if 语句中使用 && 和 || 需要多对方括号
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if [ $Name == "Steve" ] && [ $Age -eq 15 ]
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then
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echo "This will run if $Name is Steve AND $Age is 15."
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fi
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if [ $Name == "Daniya" ] || [ $Name == "Zach" ]
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then
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echo "This will run if $Name is Daniya OR Zach."
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fi
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# 表达式的格式如下:
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echo $(( 10 + 5 ))
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@ -88,18 +120,54 @@ ls -l # 列出文件和目录的详细信息
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# 用下面的指令列出当前目录下所有的 txt 文件:
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ls -l | grep "\.txt"
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# 重定向输入和输出(标准输入,标准输出,标准错误)。
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# 以 ^EOF$ 作为结束标记从标准输入读取数据并覆盖 hello.py :
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cat > hello.py << EOF
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#!/usr/bin/env python
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from __future__ import print_function
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import sys
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print("#stdout", file=sys.stdout)
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print("#stderr", file=sys.stderr)
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for line in sys.stdin:
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print(line, file=sys.stdout)
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EOF
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# 重定向可以到输出,输入和错误输出。
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python2 hello.py < "input.in"
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python2 hello.py > "output.out"
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python2 hello.py 2> "error.err"
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python hello.py < "input.in"
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python hello.py > "output.out"
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python hello.py 2> "error.err"
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python hello.py > "output-and-error.log" 2>&1
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python hello.py > /dev/null 2>&1
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# > 会覆盖已存在的文件, >> 会以累加的方式输出文件中。
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python hello.py >> "output.out" 2>> "error.err"
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# 覆盖 output.out , 追加 error.err 并统计行数
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info bash 'Basic Shell Features' 'Redirections' > output.out 2>> error.err
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wc -l output.out error.err
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# 运行指令并打印文件描述符 (比如 /dev/fd/123)
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# 具体可查看: man fd
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echo <(echo "#helloworld")
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# 以 "#helloworld" 覆盖 output.out:
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cat > output.out <(echo "#helloworld")
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echo "#helloworld" > output.out
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echo "#helloworld" | cat > output.out
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echo "#helloworld" | tee output.out >/dev/null
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# 清理临时文件并显示详情(增加 '-i' 选项启用交互模式)
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rm -v output.out error.err output-and-error.log
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# 一个指令可用 $( ) 嵌套在另一个指令内部:
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# 以下的指令会打印当前目录下的目录和文件总数
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echo "There are $(ls | wc -l) items here."
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# 反引号 `` 起相同作用,但不允许嵌套
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# 优先使用 $( ).
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echo "There are `ls | wc -l` items here."
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# Bash 的 case 语句与 Java 和 C++ 中的 switch 语句类似:
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case "$VARIABLE" in
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case "$Variable" in
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# 列出需要匹配的字符串
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0) echo "There is a zero.";;
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1) echo "There is a one.";;
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@ -107,11 +175,37 @@ case "$VARIABLE" in
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esac
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# 循环遍历给定的参数序列:
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# 变量$VARIABLE 的值会被打印 3 次。
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# 注意 ` ` 和 $( ) 等价。seq 返回长度为 3 的数组。
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for VARIABLE in `seq 3`
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# 变量$Variable 的值会被打印 3 次。
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for Variable in {1..3}
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do
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echo "$VARIABLE"
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echo "$Variable"
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done
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# 或传统的 “for循环” :
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for ((a=1; a <= 3; a++))
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do
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echo $a
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done
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# 也可以用于文件
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# 用 cat 输出 file1 和 file2 内容
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for Variable in file1 file2
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do
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cat "$Variable"
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done
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# 或作用于其他命令的输出
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# 对 ls 输出的文件执行 cat 指令。
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for Output in $(ls)
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do
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cat "$Output"
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done
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# while 循环:
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while [ true ]
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do
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echo "loop body here..."
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break
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done
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# 你也可以使用函数
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@ -132,17 +226,52 @@ bar ()
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}
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# 调用函数
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foo "My name is" $NAME
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foo "My name is" $Name
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# 有很多有用的指令需要学习:
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tail -n 10 file.txt
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# 打印 file.txt 的最后 10 行
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head -n 10 file.txt
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tail -n 10 file.txt
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# 打印 file.txt 的前 10 行
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sort file.txt
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head -n 10 file.txt
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# 将 file.txt 按行排序
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uniq -d file.txt
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sort file.txt
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# 报告或忽略重复的行,用选项 -d 打印重复的行
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cut -d ',' -f 1 file.txt
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uniq -d file.txt
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# 打印每行中 ',' 之前内容
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cut -d ',' -f 1 file.txt
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# 将 file.txt 文件所有 'okay' 替换为 'great', (兼容正则表达式)
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sed -i 's/okay/great/g' file.txt
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# 将 file.txt 中匹配正则的行打印到标准输出
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# 这里打印以 "foo" 开头, "bar" 结尾的行
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grep "^foo.*bar$" file.txt
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# 使用选项 "-c" 统计行数
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grep -c "^foo.*bar$" file.txt
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# 如果只是要按字面形式搜索字符串而不是按正则表达式,使用 fgrep (或 grep -F)
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fgrep "^foo.*bar$" file.txt
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# 以 bash 内建的 'help' 指令阅读 Bash 自带文档:
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help
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help help
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help for
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help return
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help source
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help .
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# 用 mam 指令阅读相关的 Bash 手册
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apropos bash
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man 1 bash
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man bash
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# 用 info 指令查阅命令的 info 文档 (info 中按 ? 显示帮助信息)
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apropos info | grep '^info.*('
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man info
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info info
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info 5 info
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# 阅读 Bash 的 info 文档:
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info bash
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info bash 'Bash Features'
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info bash 6
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info --apropos bash
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```
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