Linux Common Commands--grep

grep 文本过滤工具

Syntax format: grep "Options" "Pattern" "File" grep [parameter] [match pattern] [find file]
Attention:
1.grep is one of the most important commands in a Linux system, and its function is to filter matching rows and data from a text file or pipeline data stream.
The matching pattern or pattern match in the 2.grep command is something you want to find, which can be a normal text symbol or a regular expression.
Parameter options:

Parameters	Description
-C	Calculates the number of rows found ' search string '
-O	Index out of matching content
-I.	Case insensitive
-N	Displays the line number of the matching content
-R	You must use this parameter when you specify that you want to find a directory rather than a file, otherwise the grep command returns information and stops the action
-V	Reverse selection, which is a row without a ' search string ' content
-L	Lists file names for file contents that conform to the specified template style
-E	Extended grep, or egrep, can be used to extend regular expressions
--color=auto	Search keywords Display color
-V	Display software version information

Case FILE:

Case one:
Examples of parameters



Note: You test some of the searches that contain regular expressions and find that EGREP can be implemented, and grep can be implemented as well. However, for example: Egrep-v "^$|#" file1.txt, grep will not be implemented because the EGREP adds the effect of the additional regular expression meta-character set, and for standard grep, when the extension metacharacters are preceded by \, grep will automatically enable the extended option-E

Case TWO:
grep regular Expression meta-character set

Character Set	Description	Case
\^	Start of anchoring lines	such as: ' ^grep ' matches all lines that begin with grep
$	End of Anchor Line	For example: ' grep$ ' matches all rows ending with grep
.	Match a character that is not a line break	such as: ' GR.P ' matches gr followed by an arbitrary character, then P
*	Match 0 or more of previous characters	such as: ' *grep ' matches all one or more spaces followed by the grep line. * Together with any character
[ ]	Matches a character in a specified range	such as: ' [gg]rep ' matches grep and grep
[^ ]	Matches a character that is not within the specified range	such as: ' [^a-fh-z]rep ' matches the beginning of a letter that does not contain a-f and h-z, immediately following the line of the rep
\(.. \)	Tag matching characters	such as: ' (Love) ', Love is marked as 1
\<	Anchoring the beginning of a word	For example: ' \<grep ' matches a line containing a word that begins with grep
\>	Anchoring the end of a word	For example: ' grep\> ' matches lines that contain words ending with grep
X{M}	Consecutive repeating characters x,m times	For example: ' O{5} ' matches rows containing 5 consecutive O
X{m,}	Continuous repetition of character X, at least m times	For example: ' O{5,} ' matches rows with at least 5 consecutive O
X{m,n}	Repeat character X, at least m times, no more than n times	such as: ' o{5,10} ' matches rows of 5-10 consecutive O
\w	Matches a literal and numeric character that is also [a-za-z0-9]	such as: ' G\w*p ' matches a G followed by 0 or more literal or numeric characters, then P
\w	The inverted form of W, matching a non-word character	such as: Dot Period, and so on. \w* can match multiple
\b	Word lock character	such as: ' \bgrep\b ' only match grep, that is, grep is only the word, both sides are spaces

Case THREE:
Common usage



Note: Empty lines and comment lines are removed
Case FOUR:
Search files recursively


Case FIVE:
Include or exclude specified files in grep search results
1.--exclude all files after the equals sign is excluded from the search results

2.--exclude-from exclude files from the FileList file list in search results

3.--include only recursively searches for the characters "and" in the specified directory file

Case SIX:
grep and Xargs using a 0-value byte suffix

Note: the-Z parameter is personally understood to suppress the line break "show content as a line", xargs-0 is to solve the problem of not "performing the display in one line" argument,-Z is usually used in conjunction with-L. (-z option to specify a value of 0 bytes as the Terminator file name (), xargs-0 reads the input and separates the file name with a value of 0 bytes Terminator)
Case Seven:
Print a line before or after matching text


Note: If there are multiple matching results, "--" will be used as a delimiter between each matching result, and the "--" delimiter will not be displayed if multiple results are connected or overlapping rows

Linux Common Commands--grep