RHCE7--using regular expressions with Gerp

Regular expressions often contain shell metacharacters (such as s, *, etc.), and it is recommended to enclose regular expressions on merriness using single quotation marks (")

1. Line positioning symbols

Beginning of position symbol ^ and line tail Locator $

#找出以s开头的行:

' ^s ' /etc/passwd

#找出以h结尾的行:

' h$ ' /etc/passwd

2. Word locator (positioning words)

#找出包含以s开头的单词的行

' \<s ' /etc/passwd

#找出包含以h结尾的单词的行

' h\> ' /etc/passwd

In the same file, the number of rows found by word positioning is greater than the number of rows found at the beginning or end of the line:

' \<s ' /etc/passwd |WC-lnotoginseng'^s' /etc/passwd |WC-  L5

3.grep Common Options

Options	Function
-I.	Use the provided regular expression: But not case-sensitive
-V	Show only rows that do not contain regular expression matches
-R	A data search that recursively matches regular expressions is applied to a set of files or directories
-A <number>	Shows the number of rows after a regular expression match
b <number>	Shows the number of rows before a regular expression match
-E	If multiple-e options are used, multiple regular expressions can be provided and used with logical OR

RHCE7--using regular expressions with Gerp