12. sed 替换增强版

原文 https://www.thegeekstuff.com/2009/09/unix-sed-tutorial-replace-text-inside-a-file-using-substitute-command/?utm_source=sitekickr&utm_medium=snip_button

语法

Syntax:

#sed 'ADDRESSs/REGEXP/REPLACEMENT/FLAGS' filename
#sed 'PATTERNs/REGEXP/REPLACEMENT/FLAGS' filename

上面的/是delimiter 就是分隔符在某些情况可以使用其他分隔符比如 @,^,| 等
这个某些情况比如要替换// 替换成 -

重点

敲黑板敲黑板!!!

FLAGS can be any of the following

g Replace all the instance of REGEXP with REPLACEMENT
g 替换一行中所有 REGEXP 的实例默认情况只匹配第一个过会看实例
n Could be any number,replace nth instance of the REGEXP with REPLACEMENT.
p If substitution was made, then prints the new pattern space.
只替换第n找到的REGEXP 实例
i match REGEXP in a case-insensitive manner. 忽略大小写
w file If substitution was made, write out the result to the given file. 将替换好的保存到文件中记住！！！只有替换了的替换了1行就只存一行替换了两行就是两行

We can use different delimiters ( one of @ % ; : ) instead of /

但是注意当使用n 的时候不能使用g

现在有一个文件

$ cat thegeekstuff.txt
# Instruction Guides
1. Linux Sysadmin, Linux Scripting etc.
2. Databases - Oracle, mySQL etc.
3. Security (Firewall, Network, Online Security etc)
4. Storage in Linux
5. Productivity (Too many technologies to explore, not much time available)
#  Additional FAQS
6. Windows- Sysadmin, reboot etc.

做练习

Substitute Word “Linux” to “Linux-Unix” Using sed s//

$ sed 's/Linux/Linux-Unix/' thegeekstuff.txt

只替换每一行的第一个Linux 变成 Linux-Unix

其余的flag 可以自行测试 :)

补充

我写了下面一个sed 命令

dingmac@modern_php$ sed '/Administration/{ s/Administration/Supervision/;:label ;n;b label; }' theGeekStuff.txt

在MAC 中} 之前一定要记得;

上面的脚本会有报错报错原因参考如下

https://discussions.apple.com/thread/2098594

sed: 1: "/Administration/{ s/Adm ...": bad flag in substitute command: ':'

原因如下

if you want a shell command line to span multiple lines, then you need to tell the shell that command is not finished when you hit RETURN.

假如在有shell命令中有跨越多行的命令时一定要按照下面的写法

sed '{
command1;
command2 # ; 符号可有可无 多个命令一行一定要有
}'

第二点 mac 不支持e 命令这里是e 命令不是e参数

#mac
dingmac@modern_php$ echo 'a' | sed 'e date'
sed: 1: "e date": invalid command code e
#Ubuntu
dingmac@ubuntu:~$ echo 'a' | sed  -n 'e date'
Wed Jan 17 11:49:38 CST 2018

12. sed 替换 增强版

重点

补充

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