linux grep regular expression

Regular expressions for 4.shell Basics 4.1 Regular strings are a string of rules 4.1grep4.1.1 Format:grep[-cinrvabc] ' word ' filename 4.1.2-c//count, indicating number of rows 4.1.3-i//Case insensitive 4.1.4-n//Display line number 4.1.5-r//traversing all subdirectories 4.1.6-v//take anti-4.1.7 -a//followed by numbers, filtering out rows that meet the requirements and the following n rows 4.1.8-b//the

Quick grasp of grep commands and Regular Expressions The Linux system comes with the GNU grep tool that supports extended regular expressions. grep is installed by default in all Linux

. () matches the entire bracketed string, which turns out to match a single character For example: Search good or glad Grep–ne ' g (oo|la) ' regular.txt () such as matching gle,gogle,google,gooogle, and so on Grep–ne ' go*gle ' regular.txt The regular expressions under

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1. grep Introduction Grep (Global Search Regular Expression (re) and print out the line, full search for regular expressions and print out rows) is a powerful text search tool, it can use regular expressions to search for text and

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many segments, while $NF is the last, and NR is the line number.5. Mathematical operations in awkAwk can also perform mathematical operations on the values of individual segments:[Email protected] ~]# awk-f: ' {(tot=tot+$3)}; END {print tot}; ' passwd 1720The end of this is to note that all the rows have been executed, which is the syntax specific to awk, in fact awk, along with SED, can be written as a script file, with their own syntax, using if judgment in awk, and for loops is OK.example, i

1. Single quotes:What can be said to be WYSIWYG: what you see in a single quote will output what. The contents of the enclosed quotation mark do not occur if the constant or the variable is replaced. 2. double quotes: Output The contents of the double quotation marks, if there are commands, variables, etc., the variables, commands will first parse the results , and then in the output of the final content, the content constant or constant is surrounded by double quotes, the variable will be re

^word the string to find is beginning with WordGrep-n "^a" Regex.txt find the first character of a line, and lose the travel numberword$ the string to be searched ends in Wordgrep-n "a$" Regex.txt finds the line with the character ending with a, and loses the travel number. Represents any single character, including spaces\ Escape Character* Repeat 0 to infinity before the first character[List] For example: P[abc]d matches include: Pad, PBD, PCD[^list], in contrast to [list], does not include an

Tags: regularOne, part of the character description:1) ^word matches the content that begins with Word Vi/vim ^ represents the beginning of a line2) word$ matches content ending in Word Vi/vim $ represents the end of a line3) ^$ indicates blank line4). Represents and can only represent any one character5) \ Escape symbol, example \. You can only represent the point itself, let the character with special meaning take off the vest and restore itself. \$.6) * Repeat 0 or more of the preceding one c

believe in learning any Linux Release Operating system people are aware of the "regular expression, extended regular expression" of the important role of learning how to use "regular expressio