"CentOS" Regular expression

1.grep[-cinvABC]  ‘word‘  filename

-C: Print the number of lines that meet the requirements

--color: Display Color

-I: Ignore case (Ignore)

-N: Output (number) at the same time as the line that meets the requirements

-V: Print rows that do not meet the requirements (take reverse)

-A: followed by a number (with or without a space), for example, –A2 to print the line that meets the requirements and the following two lines (after)

-B: followed by a number, such as –B2, to print the line that meets the requirements and the above two lines (before)

-C: followed by a number, such as –C2, to print the line that meets the requirements and two rows above and below

-e: Allow extended regular Expressions (extended regular expression)

-R: Traversal

Note: "." means any one character eg:grep-e ' ro.t ' 1.txt= egrep ' ro.t ' 1.txt, can filter out root

". *" means 0 or more arbitrary characters, eg:grep-e ' ro.*t ' 1.txt= egrep ' ro.*t ' 1.txt, can filter out rot,rosadat,roo...t

"?" Represents 0 or one character followed in front of him, Eg:grep-e ' ro?t ' 1.txt = Egrep ' ro?t ' 1.txt, "O?" You can filter out the Rt,rot (when you think. * What do you mean, manual funny)

"+" denotes one or more of the preceding characters, eg:grep-e ' ro+t ' 1.txt = Egrep ' ro+t ' 1.txt, "o+" can filter rot,root,rooo...t

You can also use this: ... (oo+)         1.txt; ... (OO) {1.txt,{} is a number indicating the number of repetitions

[^a]:[] The ^ in parentheses means except for: Which means to take the opposite and the non

2.sed (Find replacement)

Find:

Sed-n ' NP ' 1.txt lists the first few lines

-N: Cancel default output

Np:n for the first few lines, listing multiple lines can ' 1,10p ', expressed as listing 1-10 rows, ' 5-$ ' lists line fifth to the end of the line

Sed-n '/root/p ' 1.txt lists rows that contain root

Multiple behaviors

Sed-n-E '/root/p '-e ' NP ' 1.txt

-E: Implementing Multiple behaviors

Delete

Sed ' 1,5d ' delete 1-5 rows

Replace

Sed ' s///g ' replacement (this is similar to vim), Eg:sed-r ' 5, $s # ([^:]+) (:. *+:) ([^:]+$) #\3\2\1# ' 1.txt, represented as the end word for replacing line fifth to the last row

-R: Allow extended regular Expressions (extended regular expression)

Note: Because the \ symbol is easy to confuse when it comes to paths, you can use #,@ instead

3.awk

"CentOS" Regular expression