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"
sed "s/my/Hao Chen's/g" pets.txt "This is Hao Chen's cat Hao Chen's cat's name is betty This is Hao Chen's dog Hao Chen's dog's name is frank This is Hao Chen's fish Hao Chen's fish's name is george This is Hao Chen's goat Hao Chen's goat's name is adam"
sed 's/^/#/g' 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
在每一行最后面加点东西：
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sed 's/$/ --- /g' 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 ---"
顺手介绍一下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
正规则表达式是一些很牛的事，比如我们要去掉某html中的tags：
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<b>This</b> is what <spanstyle="text-decoration: underline;">I</span> meant. Understand?
看看我们的sed命令
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# 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：
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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。
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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"
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cat 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"
只替换每一行的第一个 s：
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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：
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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：
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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"
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）
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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：
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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"
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
让我们回到最一开始的例子pets.txt，让我们来看几个命令：
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：
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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：
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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，
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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：
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# 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 "1 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：
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# 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"
下面这个例子是对每一行都挺插入：
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sed "/my/a ----" 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 ----"
c 命令
c 命令是替换匹配行
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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
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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,$d' my.txt "This is my cat, my cat's name is betty"
# 匹配fish并输出，可以看到fish的那一行被打了两遍， # 这是因为sed处理时会把处理的信息输出 sed '/fish/p' my.txt "This is my cat, my cat's name is betty This is my dog, my dog's name is frank This is my fish, my fish's name is george This is my fish, my fish's name is george This is my goat, my goat's name is adam"
# 使用n参数就好了 sed -n '/fish/p' my.txt "This is my fish, my fish's name is george"
# 从一个模式到另一个模式 sed -n '/dog/,/fish/p' my.txt "This is my dog, my dog's name is frank This is my fish, my fish's name is george"
#从第一行打印到匹配fish成功的那一行 sed -n '1,/fish/p' my.txt "This is my cat, my cat's name is betty This is my dog, my dog's name is frank This is my fish, my fish's name is george"
bool bexec = false foreach line in file { if ( match(address1) ){ bexec = true; }
if ( bexec == true) { EXEC(sed_cmd); }
if ( match (address2) ) { bexec = false; } }
关于address可以使用相对位置，如：
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# 其中的+3表示后面连续3行 sed '/dog/,+3s/^/# /g' pets.txt "This is my cat my cat's name is betty # This is my dog # my dog's name is frank # This is my fish # my fish's name is george This is my goat my goat's name is adam"
cat pets.txt "This is my cat my cat's name is betty This is my dog my dog's name is frank This is my fish my fish's name is george This is my goat my goat's name is adam"
# 对3行到第6行，执行命令/This/d sed '3,6 {/This/d}' pets.txt "This is my cat my cat's name is betty my dog's name is frank my fish's name is george This is my goat my goat's name is adam"
# 对3行到第6行，匹配/This/成功后，再匹配/fish/，成功后执行d命令 sed '3,6 {/This/{/fish/d}}' pets.txt "This is my cat my cat's name is betty This is my dog my dog's name is frank my fish's name is george This is my goat my goat's name is adam"
# 从第一行到最后一行，如果匹配到This，则删除之；如果前面有空格，则去除空格 sed '1,${/This/d;s/^ *//g}' pets.txt "my cat's name is betty my dog's name is frank my fish's name is george my goat's name is adam"
