技术标签: linux服务器相关 sed awk
awk于1977年出生,今年36岁本命年,sed比awk大2-3岁,awk就像林妹妹,sed就是宝玉哥哥了。所以 林妹妹跳了个Topless,他的哥哥sed坐不住了,也一定要出来抖一抖。
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。
同样,本篇文章不会说sed的全部东西,你可以参看sed的手册,我这里主要还是想和大家竞争一下那些从手机指缝间或马桶里流走的时间,用这些时间来学习一些东西。当然,接下来的还是要靠大家自己双手。
我使用下面的这段文本做演示:
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$
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):
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$
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
|
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:
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$
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:
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$
sed
-i
"s/my/Hao Chen's/g"
pets.txt
|
在每一行最前面加点东西:
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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
|
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:
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 <
span
style
=
"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
|
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)
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$
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
|
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…)
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$
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
让我们回到最一开始的例子pets.txt,让我们来看几个命令:
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
"$ 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
|
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
|
打印命令
你可以把这个命令当成grep式的命令
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# 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
|
好了,下面我们要介绍四个sed的基本知识点:
第零个是关于-n参数的,大家也许没看懂,没关系,我们来看一下sed处理文本的伪代码,并了解一下Pattern Space的概念:
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foreach line in file {
//放入把行Pattern_Space
Pattern_Space <= line;
// 对每个pattern space执行sed命令
Pattern_Space <= EXEC(sed_cmd, Pattern_Space);
// 如果没有指定 -n 则输出处理后的Pattern_Space
if
(sed option hasn't
"-n"
) {
print Pattern_Space
}
}
|
第一个是关于address,几乎上述所有的命令都是这样的(注:其中的!表示匹配成功后是否执行命令)
[address[,address]][!]{cmd}
address可以是一个数字,也可以是一个模式,你可以通过逗号要分隔两个address 表示两个address的区间,参执行命令cmd,伪代码如下:
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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
|
第二个是cmd可以是多个,它们可以用分号分开,可以用大括号括起来作为嵌套命令。下面是几个例子:
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$
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,${/This/d;s/^ *//g}'
pets.txt
my
cat
's name is betty
my dog's name is frank
my fish's name is george
my goat's name is adam
|
第三个我们再来看一下 Hold Space
接下来,我们需要了解一下Hold Space的概念,我们先来看四个命令:
g: 将hold space中的内容拷贝到pattern space中,原来pattern space里的内容清除
G: 将hold space中的内容append到pattern space\n后
h: 将pattern space中的内容拷贝到hold space中,原来的hold space里的内容被清除
H: 将pattern space中的内容append到hold space\n后
x: 交换pattern space和hold space的内容
这些命令有什么用?我们来看两个示例吧,用到的示例文件是:
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$
cat
t.txt
one
two
three
|
第一个示例:
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$
sed
'H;g'
t.txt
one
one
two
one
two
three
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是不是有点没看懂,我作个图你就看懂了。
第二个示例,反序了一个文件的行:
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$
sed
'1!G;h;$!d'
t.txt
three
two
one
|
其中的 ‘1!G;h;$!d’ 可拆解为三个命令
这个执行序列很难理解,做个图如下大家就明白了:
就先说这么多吧,希望对大家有用。
(全文完)
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文章浏览阅读997次。散射光能量和入射光频率的4次方成正比,所以蓝光紫光比红光更容易被散射_光线散射 公式
文章浏览阅读541次。Shape of HDUTime Limit: 3000/1000 MS (Java/Others) Memory Limit: 32768/32768 K (Java/Others)Total Submission(s): 7061 Accepted Submission(s): 3200Problem Description话说上回讲到海东集团推选老总的_hdu 2108 shape of hdu
文章浏览阅读133次。但是,智能照明在我国一直没有引起足够的重视,大部分建筑物采用的照明依然是传统的照明控制方式,因此,本文就智能照明系统在现代建筑中的应用进行分析, 继而使人们认识智能照明系统的优点,为其发展提供一些推动作用。智能化已经成为全球建筑发展的主流技术,其涵盖多个方面。在现代建筑中, 智能照明系统的设备不但多而且比较分散,待实现的控制功能较多,因而如何构建经济 合理、实用的智能照明系统,如何确定智能照明系统在现代建筑照明中的控制策略 是亟待解决的问题,只有把这些问题解决了,智能照明系统才能够在现代建筑中广泛的应用。
文章浏览阅读683次。基于CMake的构建系统(buildsystem),其组织形式是一组高级逻辑目标(high-level logical targets)。每个目标(target)对应于一个可执行文件或库,或者一个包含自定义命令的自定义目标。构建系统说明了目标之间的依赖关系,从而确定构建顺序和响应更改时的重生成规则。_install_interface
文章浏览阅读788次,点赞9次,收藏28次。先使用命令/usr/local/nginx/sbin/nginx -V 查看已安装的 Nginx 是否包HTTP_STUB_STATUS 模块,cat /opt/nginx-1.12.0/auto/options | grep YES #查看nginx已安装的所有模块。在Linux平台.上,在进行高并发TCP连接处理时,最高的并发数量都要受到系统对用户单一进程同时可打开文件数量的限制(这是因为系统为每个TCP连接都要创建一个socket句柄,每个socket句柄同时也是一个文件句柄)。
文章浏览阅读2.7w次,点赞211次,收藏852次。某高校欲开发一个成绩管理系统,记录并管理所有选修课程的学生的平时成绩和考试成绩,其主要功能描述如下: 1. 每门课程都有3到6个单元构成,每个单元结束后会进行一次测试,其成绩作为这门课程的平时成绩。课程结束后进行期末考试,其成绩作为这门课程的考试成绩。 2. 学生的平时成绩和考试成绩均由每门课程的主讲教师上传给成绩管理系统。 3. 在记录学生成绩之前,系统需要验证这些成绩是否有效。首先..._招聘考试成绩管理数据流程图