Grep命令主要用于从文件中查找指定的字符串。
建一个demo_file:
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例01:从单个文件中查找指定的字符串
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例02:从多个文件中查找指定的字符串
复制代码代码如下:
$ cp demo_file demo_file1
$ grep "this" demo_
demo_file:this le is the 1st lower case le this file.
demo_file:Two les above this le is empty.
demo_file:And this is the last le.
demo_file1:this le is the 1st lower case le this file.
demo_file1:Two les above this le is empty.
demo_file1:And this is the last le.
例03:忽略大小写使用 grep -i
复制代码代码如下:
$ grep -i "the" demo_file
THIS LINE IS THE 1ST UPPER CASE LINE IN THIS FILE.
this le is the 1st lower case le this file.
This Le Has All Its First Character Of The Word With Upper Case.
And this is the last le.
例04:在文件中匹配正则表达式
如果你能在实际使用正则表达式，能使效率大大提高。在下面的例子中，匹配了所有以les开头，以empty结尾的行。
复制代码代码如下:
$ grep "les.empty" demo_file
Two les above this le is empty.
从Grep文档的来看，一个正则表达式必须遵循下面的匹配操作。
1.? The precedg item is optional and matched at most once.
2. The precedg item will be matched zero or more times.
3.+ The precedg item will be matched one or more times.
4.{n} The precedg item is matched exactly n times.
5.{n,} The precedg item is matched n or more times.
6.{,m} The precedg item is matched at most m times.
7.{n,m} The precedg item is matched at least n times, but not more than m times.
例05:用grep -w来查找全匹配，不包括子字符串
比如说:用下面的例子搜索出来的例子包括"is","his"
复制代码代码如下:
$ grep -i "is" demo_file
THIS LINE IS THE 1ST UPPER CASE LINE IN THIS FILE.
this le is the 1st lower case le this file.
This Le Has All Its First Character Of The Word With Upper Case.
Two les above this le is empty.
And this is the last le.
而用grep -iw搜索出来的结果如下: 注意，忽略大小。"IS","is"
复制代码代码如下:
$ grep -iw "is" demo_file
THIS LINE IS THE 1ST UPPER CASE LINE IN THIS FILE.
this le is the 1st lower case le this file.
Two les above this le is empty.
And this is the last le.
例06:用grep -A,-B,-C 来查看after/before/around 行
当在一个大的文件中执行grep操作时，如果想要看其中一些行，并且想看之前，之后的或某些行附近的，那么这里命令就起作用了。grep -A,-B,-C.先建个demo.txt作为模板
复制代码代码如下:
$ cat demo_text
4. Vim Word Navigation
You may want to do several navigation relation to the words, such as:
e - go to the end of the current word.
E - go to the end of the current WORD.
b - go to the previous (before) word.
B - go to the previous (before) WORD.
w - go to the next word.
W - go to the next WORD.
WORD - WORD consists of a sequence of non-blank characters, separated with white space.
word - word consists of a sequence of letters, digits and underscores.
Example to show the difference between WORD and word
192.168.1.1 - sgle WORD
192.168.1.1 - seven words.
6.1 显示匹配后N行
复制代码代码如下:
$ grep -A 3 -i "example" demo_text
Example to show the difference between WORD and word
192.168.1.1 - sgle WORD
192.168.1.1 - seven words.
6.2 显示匹配前N行
复制代码代码如下:
$ grep -B 2 "sgle WORD" demo_text
Example to show the difference between WORD and word
192.168.1.1 - sgle WORD
6.3 显示匹配前N行
复制代码代码如下:
$ grep -C 2 "Example" demo_text
word - word consists of a sequence of letters, digits and underscores.
Example to show the difference between WORD and word
192.168.1.1 - sgle WORD
例07:用GREP_OPTIONS来让查找的项醒目
如果你想使匹配的好看且醒目，可以使用下面的操作:
复制代码代码如下:
$ export GREP_OPTIONS='--color=auto' GREP_COLOR='100;8'
$ grep this demo_file
this le is the 1st lower case le this file.
Two les above this le is empty.
And this is the last le.
例08:用grep -r来搜索所有的文件及子目录
复制代码代码如下:
$ grep -r "ramesh"
例09:用grep -v来显示不匹配的项
复制代码代码如下:
$ grep -v "go" demo_text
4. Vim Word Navigation
You may want to do several navigation relation to the words, such as:
WORD - WORD consists of a sequence of non-blank characters, separated with white space.
word - word consists of a sequence of letters, digits and underscores.
Example to show the difference between WORD and word
192.168.1.1 - sgle WORD
192.168.1.1 - seven words.
例10:显示所有不匹配的项
复制代码代码如下:
$ cat test-file.txt
a
b
c
d
$ grep -v -e "a" -e "b" -e "c" test-file.txt
d
例11:用grep -c 来计算匹配的数量
11.1计算匹配的字符串数
复制代码代码如下:
$ grep -c "go" demo_text
6
11.2计算匹配的模式数
复制代码代码如下:
$ grep -c this demo_file
3
11.3计算不匹配的模式数
复制代码代码如下:
$ grep -v -c this demo_file
4
例12:使用grep -l显示匹配的文件名
复制代码代码如下:
$ grep -l this demo_
demo_file
demo_file1
例13:只显示匹配的字符串
复制代码代码如下:
$ grep -o "is.le" demo_file
is le is the 1st lower case le
is le
is is the last le
例14:
复制代码代码如下:
$ cat temp-file.txt1234512345
$ grep -o -b "3" temp-file.txt
2:3
8:3
注意:上述的不是该字符所在行中的位置，而是字节的位置。
例15:用grep -n 显示行数
复制代码代码如下:
$ grep -n "go" demo_text
5: e - go to the end of the current word.
6: E - go to the end of the current WORD.
7: b - go to the previous (before) word.
8: B - go to the previous (before) WORD.
9: w - go to the next word.
10: W - go to the next WORD.