Linux下常用的12个grep命令范例
Have you ever been confronted with the task of looking for a
particular string or pattern in a file, yet have no idea where to
start looking? Well then, here is grep to the rescue!
你是否面临过查找特殊字符的文件去不知从何下手?那么,就让grep命令来帮助你吧!
grep is a powerful file pattern searcher that comes equipped on
every distribution of Linux. If, for whatever reason, it is not
installed on your system, you can easily install it via your package
manager (apt-get on Debian/Ubuntu and yum on RHEL/CentOS/Fedora).
grep
命令是配备在每一个Linux发行版中的功能强大的文件搜索功能.如果某种原因你的系统没有安装,你可以通过系统携带的包安装器来安装它
(apt-get on Debian/Ubuntu and yum on RHEL/CentOS/Fedora).
$ sudo apt-get install grep #Debian/Ubuntu
$ sudo yum install grep #RHEL/CentOS/FedoraI have found that the easiest way to get your feet wet with grep is to
just dive right in and use some real world examples.
我发现在grep的世界中把脚弄湿的最简单方法就是直接去潜水….(咋翻译呀)
Let’s say that you have just installed a fresh copy of the new Ubuntu
on your machine, and that you are going to give Python scripting a
shot. You have been scouring the web looking for tutorials, but you
see that there are two different versions of Python in use, and you
don’t know which one was installed on your system by the Ubuntu
installer, or if it installed any modules. Simply run this command:
假设你的机器上安装了最新的Ubuntu系统,你需要给Python脚本一个快照,你一直在网上找相关的教程,但是你看到了两个不同的Python版本,你不知道哪一下是Ubuntu系统安装的.你可以运行以下命令:(翻译得太烂了)
# dpkg –l | grep –i python
Sample Output
ii python2.7 2.7.3-0ubuntu3.4 Interactive high-level object-oriented language (version 2.7)
ii python2.7-minimal 2.7.3-0ubuntu3.4 Minimal subset of the Python language (version 2.7)
ii python-openssl 0.12-1ubuntu2.1 Python wrapper around the OpenSSL library
ii python-pam 0.4.2-12.2ubuntu4 A Python interface to the PAM libraryFirst, we ran dpkg –l, which lists installed *.deb packages on
your system. Second, we piped that output to grep –i python, which
simple states “go to grep and filter out and return everything with
‘python’ in it.” The –i option is there to ignore-case, as grep is
case-sensitive. Using the –i option is a good habit of getting into,
unless of course you are trying to nail down a more specific search.
首先我们运行dpkg -l,会列出系统中安装过的*.deb包.
然后我们通过管道输出 grep –i
python,这个意思是”通过grep过滤出含有python并返回.”
-i选项是忽略大小写(grep
命令是区分大小写的),用-i选项是一个良好的习惯,除非你在进行一个更具体的搜索
The grep can also be used to search and filter within individual files
or multiple files. Lets take this scenario:
grep命令也可以对单个或多个文件进行搜索过滤.假设如下场景:
You are having some trouble with your Apache Web Server, and you have
reached out to one of the many awesome forums on the net asking for
some help. The kind soul who replies to you has asked you to post the
contents of your /etc/apache2/sites-available/default-ssl file.
Wouldn’t it be easier for you, the guy helping you, and everyone
reading it, if you could remove all of the commented lines? Well you
can! Just run this:
你的Apache Web Server 遇到了一些麻烦,你通过一些相关论坛寻找帮助.The
kind
soul(不会翻译)回复你说需要你查看你/etc/apache2/sites-available/default-ssl文件的内容.如果能去除掉文件中所有的注释行,会对这些查看文件并帮助你的人更容易些.你可以运行:
# grep –v “#” /etc/apache2/sites-available/default-sslThe –v option tells grep to invert its output, meaning that
instead of printing matching lines, do the opposite and print all of
the lines that don’t match the expression, in this case, the #
commented lines.
-v 选项的意思是反转输出,即输入不匹配的行.在这里就是输出不含有#的行.
The grep can be very useful for filtering from stdout. For example,
let’s say that you have an entire folder full of music files in a
bunch of different formats. You want to find all of the *.mp3 files
from the artist JayZ, but you don’t want any of the remixed tracks.
Using a find command with a couple of grep pipes will do the trick:
grep可以非常有用从标准输出中过滤.例如,你有一个音乐文件夹中含有各中不同的格式.你想找出艺术家JayZ的*.mp3文件,但是又不想要任何含有混音的曲目.你可以利用find和grep管道来处理:
# find . –name “*.mp3” | grep –i JayZ | grep –vi “remix”In this example, we are using find to print all of the files with a
*.mp3 extension, piping it to grep –i to filter out and prints all
files with the name “JayZ” and then another pipe to grep –vi which
filters out and does not print all filenames with the string (in any
case) “remix”.
这里我们先打印出所有*.mp3文件,利用grep管道过滤出名字中含有”JayZ”再利用grep
-vi过滤出不含有”remix”的文件
Another couple of options are the –A and –B switches, which displays
the matched line and number of lines either that come before or after
the search string. While the man page gives a more detailed
explanation, I find it easiest to remember the options as –A = after,
and –B = before:
另外一对选项 -A -B 它会显示匹配的前或后数字行. 在man
page中可以查看到更多的解释.可以理解成–A = after –B =
before更容易一些:
# ifconfig | grep -A4 eth0
# ifconfig | grep -B2 UPThe grep’s –C option is similar, but instead of printing the lines
that come either before or after the string, it prints the lines in
either direction:
grep的-C选项与上面-A
-B类似.但是此选项会同时打印出前后两个方向上的数字行:
# ifconfig | grep -C2 loSimilar to piping a grep string to word count (wc program) grep’s
built-in option can perform the same for you:
类似grep管道的统计(wc) 可以执行grep的内置选项:
# ifconfig | grep –c inet6The –n option for grep is very useful when debugging files during
compile errors. It displays the line number in the file of the given
search string:
在编译错误调试过程中 grep -n选项是非常有用的.它会显示搜索内容的行号:
# grep –n “main” setup..pyIf you would like to search for a string in the current directory
along with all of the subdirectories, you can specify the –r option to
search recursively:
如果你想搜索当前文件夹和其子文件夹,你可能用-r选项上来递归搜索:
# grep –r “function” *Passing the –w option to grep searches for the entire pattern that is
in the string. For example, using:
通过-w 选项你可以搜索字符串整个模式:(不知道怎么翻译了):
ifconfig | grep -w "RUNNING"
ifconfig | grep -w "RUN"
什么也不会返回.除非是整个单词.Deserving some mention are grep’s derivatives. The first is zgrep,
which, similar to zcat, is for use on gzipped files. It takes the same
options as grep and is used in the same way:
这里值得提出来的是grep的衍生品,第一是 zgrep ,类似 zcat,用于gzip文件.
操作和选项和grep是一样的:
# zgrep –i error /var/log/syslog.2.gzThe egrep is another derivative that stands for “Extended Global
Regular Expression”. It recognizes additional expression
meta-characters such at + ? | and (). egrep is very useful for
searching source files, and other pieces of code, should the need
arise. It can be invoked from regular grep by specifying the –E
option.
另一个衍生品是egrep
其全称是”全局扩展正则表达式”,它可以识别更多的表达式和无字符.例如+ ? |
and () .egrep 在搜索代码和源文件的时候非常有用.grep
可以通过-E选项来使用.
# grep –EThe fgrep searches a file or list of files for a fixed pattern string.
It is the same as grep –F. A common way of using fgrep is to pass a
file of patterns to it:
fgrep 通过一个或多个文件来匹配搜索,可以如 grep
-F将匹配模式文件传递给它:
# fgrep –f file_full_of_patterns.txt file_to_search.txtThis is just a starting point with grep, but as you are probably able
to see, it is invaluable for a variety of purposes. Aside from the
simple one line commands we have implemented, grep can be used to
write powerful cron jobs, and robust shell scripts, for a start. Be
creative, experiment with the options in the man page, and come up
with grep expressions that serve your own purposes!
这只是grep的一个开端,正如你可以看到的那样.它可以用在各种用途.除了我们上面简单的例子.grep可以用编写强大的cron任务和shell脚本,只要有创意.你可以通过man
page中的相关选项,编写出符合你自己目的的grep.
http://www.tecmint.com/12-practical-examples-of-linux-grep-command/