grep is a powerful text-search tool that uses regular expressions to search for text and print matching lines
grep [option] [mode] [file]
-C #只输出匹配行的数量
-I. #搜索时忽略大小写
-H #查询多文件时不显示文件名
-L #只列出符合匹配的文件名 instead of listing specific matching rows
-N#列出所有的匹配行 and displays the line number
-S#不显示不存在或无匹配文本的错误信息
-V#显示不包含匹配文本的所有行
-W#匹配整词
-X#匹配整行
-R#递归搜索 not only search the current working directory, but also search subdirectories
-Q#禁止输出任何结果, the exit status indicates whether the search was successful
-B#打印匹配行距文件头部的偏移量, in your own unit
-O#与-B option to print the offset of the matched word from the head in bytes, in combination with
-E#支持扩展的正则表达式
-F#不支持正则表达式, match the literal meaning of the string
Grep-c root/etc/passwd #文本中有两个root匹配, which shows the number of rows is 2
Grep-i XXX 1#文本中有XXX和xxx,-I will ignore the case after the output.
Grep-h Root/etc/passwd/etc/shadow#原本查询多文件时, the match will show the file name and matching rows, and only the matching rows will be displayed after the plus-H, without showing which file matches
Grep-l Root/etc/passwd/etc/shadowOnly matching file names are displayed after #加-L, not specific matching rows
Grep-n root/etc/passwd#-n matches the line number in front of the output match result
Grep-s root/etc/passwd#不显示错误信息, for example: grep ROOT/ETC/PASSWDWDWD
Grep-v root/etc/passwd #列出除了匹配行root以外的所有行
Grep-w root/etc/passwd #列出文件中有单个root的单词的行
Grep-x root/etc/passwd #列出文件中有单个root为整行的行
Grep-r root/tmp#列出 root in/tmp under root and subdirectory files, recursively query out all root characters
Grep-q Root/tmp/root #不输出任何信息, with the Exit method, success is 0, unsuccessful for other values
GREP-VC Root/etc/passwd/etc/shadow #显示出文件pass和sha中有多少行是不包含root的行
1. Match the beginning of the line
(1), search "/etc/passwd" in the beginning of "root" line, and print travel number
Grep-n ^root/etc/passwd
(2), retrieve the blank line in the "/etc/services" file, and list the line number. Retrieving empty lines again with a few lines
Grep-n ^$/etc/services
Grep-c ^$/etc/services
(3), the search file begins with "-", and repeats any time, followed by the D-Character matching line
Search file with "/" Start, Intermediate "4" any characters, the "6" character is still "/" matching line
grep ^-*d filename
grep ^/..../filename
(4), Search for "sed.edu.cn" matching line
grep sed\.edu\.cn
(5), search "-" symbol repeated 5 times the line of text
Search for "the" line that matches exactly
Features of grep ' \-\{5\} ' filename #考验 ' and \{\} expressions
Features of grep ' \<the\> ' filename #考验 ' and \<\> expressions
grep #标准grep命令. Support for regular expressions
Egrep #扩展grep命令. Support for basic and extended regular expressions
Fgrep #快速grep命令. Regular expressions are not supported and are matched by the literal meaning of the string
Egrep Command and GREP-E equivalence
Fgrep Command and Grep-f equivalence
Analyze what the following regular expression means
(1), kk* grep kk* test #列出文件test包含kK及后面有任意多个字符的行
(2), k\{6,8\} grep ' k\{6,8\} ' test #列出文件test中k单词重复6-8 rows
(3), k\{6,\} grep ' k\{6,\} ' test #列出文件test中k单词大于6个的行
(4), k\{10\} grep ' k\{6\} ' test #列出文件test中k单词为6个的行
(5), ^new year$
(6), ^$#空行
(7), [0-9][0-9][a-z] grep [0-9][0-9][a-z] File #列出文件中前两个字符为数字, the next character is a matching line of letters
(8), [a-h]\{1,3\},[0-9]\{5\} #grep ' [a-h]\{1,3\} ' Test | grep ' [0-9]\{5\} ' #列出1-3 a-h words, 5 digits of a character
(9), ^\ ...
(10), [^p-z]*\. #列出除了p a line of any character other than-Z
2. Use the wildcard function to list all numbers starting with a number, and the last 3 to be a period and 2 of any letter of the file name
[0-9]*[a-z]\{2\} ...
3. View the following three commands
Grep-c ^$ filename #列出空行的数目
Grep-c ^[^$] FileName #列出非空行的数目
GREP-C ^^ $ filename
4. Count the number of blank rows in the current directory and all files under subdirectories
Grep-r ^$/root/| Wc-l
5. Count the number of rows that contain non-blank rows for all files in the current directory and sub-directories
Grep-r ^[^$]/root/| Wc-l
6, the combination of the description of the symbol, to observe whether the right and wrong
Grep-n-\{5,\} file #缺引号, missing escape character \-
Grep-n '-\{5,\} ' file #缺转义符, system default does not know-yes option
Grep-n ' \-\{5,\} ' file #正确
Shell Programming---grep command
