linux - sed

sed全名叫stream editor，流编辑器，用程序的方式来编辑文本，相当的hacker啊。sed基本上就是玩正则模式匹配，所以，玩sed的人，正则表达式一般都比较强。

用s命令替换

使用下面的这段文本做演示：

$ cat pets.txt
This is my cat
my cat's name is betty
This is my dog
my dog's name is frank
This is my fish
my fish's name is george
This is my goat
my goat's name is adam

把其中的my字符串替换成Hao Chen’s，下面的语句应该很好理解（s表示替换命令，/my/表示匹配my，/Hao Chen’s/表示把匹配替换成Hao Chen’s，/g 表示一行上的替换所有的匹配）：

把其中的my字符串替换成Hao Chen’s，下面的语句应该很好理解（s表示替换命令，/my/表示匹配my，/Hao Chen’s/表示把匹配替换成Hao Chen’s，/g 表示一行上的替换所有的匹配）：

注意：如果你要使用单引号，那么你没办法通过\’这样来转义，就有双引号就可以了，在双引号内可以用\”来转义。

再注意：上面的sed并没有对文件的内容改变，只是把处理过后的内容输出，如果你要写回文件，你可以使用重定向，如：

$ sed"s/my/Hao Chen's/g"pets.txt > hao_pets.txt

或使用 -i 参数直接修改文件内容：

$ sed -i "s/my/Hao Chen's/g" pets.txt

正则表达式的一些最基本的东西

• ^ 表示一行的开头。如：/^#/ 以#开头的匹配。
• $ 表示一行的结尾。如：/}$/ 以}结尾的匹配。
• \< 表示词首。 如 \<abc 表示以 abc 为首的詞。
• \> 表示词尾。 如 abc\> 表示以 abc 結尾的詞。
• . 表示任何单个字符。
• * 表示某个字符出现了0次或多次。
• [ ] 字符集合。 如：[abc]表示匹配a或b或c，还有[a-zA-Z]表示匹配所有的26个字符。如果其中有^表示反，如[^a]表示非a的字符

去掉某html中的tags：

html.txt

< code>b<This</>b< is what < code>spanstyle="text-decoration: underline;"<I</>span< meant. Understand?

看看我们的sed命令

# 如果你这样搞的话，就会有问题

$ sed 's/< >//g' html.txt
Understand?

# 要解决上面的那个问题，就得像下面这样。

# 其中的'[^<]' 指定了除了<的字符重复0次或多次。

$ sed 's/<[^>]*>//g' html.txt
This is what I meant. Understand?

我们再来看看指定需要替换的内容：

$ sed"3s/my/your/g"pets.txt
This is my cat
my cat's name is betty
This is your dog
my dog's name is frank
This is my fish
my fish's name is george
This is my goat
my goat's name is adam

下面的命令只替换第3到第6行的文本。

$ sed "3,6s/my/your/g"pets.txt
This is my cat
my cat's name is betty
This is your dog
your dog's name is frank
This is your fish
your fish's name is george
This is my goat
my goat's name is adam

只替换每一行的第一个s：

$ sed 's/s/S/1' my.txt
ThiS is my cat, my cat's name is betty
ThiS is my dog, my dog's name is frank
ThiS is my fish, my fish's name is george
ThiS is my goat, my goat's name is adam

只替换每一行的第二个s：

$ sed's/s/S/2'my.txt
This iS my cat, my cat's name is betty
This iS my dog, my dog's name is frank
This iS my fish, my fish's name is george
This iS my goat, my goat's name is adam

只替换第一行的第3个以后的s：

$ sed's/s/S/3g'my.txt
This is my cat, my cat'S name iS betty
This is my dog, my dog'S name iS frank
This is my fiSh, my fiSh'S name iS george
This is my goat, my goat'S name iS adam

多个匹配

如果我们需要一次替换多个模式，可参看下面的示例：（第一个模式把第一行到第三行的my替换成your，第二个则把第3行以后的This替换成了That）

$ sed '1,3s/my/your/g; 3,$s/This/That/g'my.txt
This is your cat, your cat's name is betty
This is your dog, your dog's name is frank
That is your fish, your fish's name is george
That is my goat, my goat's name is adam

上面的命令等价于：（注：下面使用的是sed的-e命令行参数）

Sed -e  '1,3s/my/your/g' -e  '3,$s/This/That/g' my.txt

我们可以使用&来当做被匹配的变量，然后可以在基本左右加点东西。如下所示：

$ sed 's/my/[&]/g' my.txt
This is [my] cat, [my] cat's name is betty
This is [my] dog, [my] dog's name is frank
This is [my] fish, [my] fish's name is george
This is [my] goat, [my] goat's name is adam

圆括号匹配

使用圆括号匹配的示例：（圆括号括起来的正则表达式所匹配的字符串会可以当成变量来使用，sed中使用的是\1,\2…）

$ sed 's/This is my \([^,]*\),.*is \(.*\)/\1:\2/g' my.txt
cat:betty
dog:frank
fish:george
goat:adam

上面这个例子中的正则表达式有点复杂，解开如下（去掉转义字符）：

正则为：This is my ([^,]*),.*is (.*)
匹配为：This is my (cat),……….is (betty)

然后：\1就是cat，\2就是betty

sed的命令

回到最一开始的例子pets.txt，让我们来看几个命令：

$ cat pets.txt
This is my cat
my cat's name is betty
This is my dog
my dog's name is frank
This is my fish
my fish's name is george
This is my goat
my goat's name is adam

N命令

先来看N命令 —— 把下一行的内容纳入当成缓冲区做匹配。

下面的的示例会把原文本中的偶数行纳入奇数行匹配，而s只匹配并替换一次，所以，就成了下面的结果：

$ sed'N;s/my/your/'pets.txt
This is your cat
my cat's name is betty
This is your dog
my dog's name is frank
This is your fish
my fish's name is george
This is your goat
my goat's name is adam

也就是说，原来的文件成了：

This is my cat\n  my cat's name is betty
This is my dog\n  my dog's name is frank
This is my fish\n  my fish's name is george
This is my goat\n  my goat's name is adam

这样一来，下面的例子你就明白了，

$ sed'N;s/\n/,/'pets.txt
This is my cat,  my cat's name is betty
This is my dog,  my dog's name is frank
This is my fish,  my fish's name is george
This is my goat,  my goat's name is adam

a命令和i命令

a命令就是append， i命令就是insert，它们是用来添加行的。如：

# 其中的1i表明，其要在第1行前插入一行（insert）
$ sed "1 i This is my monkey, my monkey's name is wukong"my.txt
This is my monkey, my monkey's name is wukong
This is my cat, my cat's name is betty
This is my dog, my dog's name is frank
This is my fish, my fish's name is george
This is my goat, my goat's name is adam
# 其中的1a表明，其要在最后一行后追加一行（append）
$ sed"$ a This is my monkey, my monkey's name is wukong"my.txt
This is my cat, my cat's name is betty
This is my monkey, my monkey's name is wukong
This is my dog, my dog's name is frank
This is my fish, my fish's name is george
This is my goat, my goat's name is adam

我们可以运用匹配来添加文本：

# 注意其中的/fish/a，这意思是匹配到/fish/后就追加一行
$ sed"/fish/a This is my monkey, my monkey's name is wukong"my.txt
This is my cat, my cat's name is betty
This is my dog, my dog's name is frank
This is my fish, my fish's name is george
This is my monkey, my monkey's name is wukong
This is my goat, my goat's name is adam

c命令

c 命令是替换匹配行

$ sed "2 c This is my monkey, my monkey's name is wukong" my.txt
This is my cat, my cat's name is betty
This is my monkey, my monkey's name is wukong
This is my fish, my fish's name is george
This is my goat, my goat's name is adam
$ sed"/fish/c This is my monkey, my monkey's name is wukong"my.txt
This is my cat, my cat's name is betty
This is my dog, my dog's name is frank
This is my monkey, my monkey's name is wukong
This is my goat, my goat's name is adam

 

d命令

删除匹配行

$ sed'/fish/d'my.txt
This is my cat, my cat's name is betty
This is my dog, my dog's name is frank
This is my goat, my goat's name is adam
$ sed'2d'my.txt
This is my cat, my cat's name is betty
This is my fish, my fish's name is george
This is my goat, my goat's name is adam
$ sed'2,$d'my.txt
This is my cat, my cat's name is betty

 

p命令

打印命令

你可以把这个命令当成grep式的命令

# 匹配fish并输出，可以看到fish的那一行被打了两遍，
# 这是因为sed处理时会把处理的信息输出
$ sed'/fish/p'my.txt
This is my cat, my cat's name is betty
This is my dog, my dog's name is frank
This is my fish, my fish's name is george
This is my fish, my fish's name is george
This is my goat, my goat's name is adam
# 使用n参数就好了
$ sed -n '/fish/p'my.txt
This is my fish, my fish's name is george
# 从一个模式到另一个模式
$ sed -n '/dog/,/fish/p'my.txt
This is my dog, my dog's name is frank
This is my fish, my fish's name is george
#从第一行打印到匹配fish成功的那一行
$ sed-n '1,/fish/p'my.txt
This is my cat, my cat's name is betty
This is my dog, my dog's name is frank
This is my fish, my fish's name is george