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This article mainly introduces "how to write a linux script to extract lines that meet certain conditions". In daily operation, I believe many people have doubts about how to write linux scripts to extract lines that meet certain conditions. The editor consulted all kinds of materials and sorted out simple and easy-to-use methods of operation. I hope it will be helpful for you to answer the questions of "how to write linux scripts to extract lines that meet certain conditions". Next, please follow the editor to study!

The difference between 1.inline and block,inline-block

Replacement elements: almost all replaceable elements are inline elements, such as

, etc.

Replacement elements generally have internal dimensions, so they have width and height, which can be set. For example, when you do not specify the width and height of img, it is displayed according to its internal size, that is, the width and height of the image when it is saved.

For form elements, browsers also have default styles, including width and height.

Irreplaceable elements:

Display:inline-block renders the object as an inline object, but the contents of the object are rendered as block objects. The next inline object will be rendered in the same line (to be exact, the element that applies this property is rendered as an inline object, and the surrounding elements remain in the same line, but the attributes of block elements such as width, height,padding,border, and margin can be set)

Inline block elements (inline-block elements) behave like block elements inside, for example, he has width, height,padding,border and margin of block elements, while the outer arrangement is similar to inline elements, that is, horizontally, rather than from top to bottom like block-level elements.

Display:inline inline elements, inline elements

Diplay:block block-level elements

How to center div in 2.CSS

The margin:0 auto element must have a width to center

If there are only two parameters after margin, the first represents top and bottom, and the second represents left and right

Because 0 auto means that the upper and lower boundaries are 0, the left and right sides are adaptive to the same value according to the width (that is, centered)

Div centered implementation

Body {text-align:center} / / parent element content centered div {margin:0 auto;} / / Child element div element is centered

The 3.linux script extracts lines that meet certain conditions

Awk binding-gt (>) or-ge (> =)

Awk'$1 > 10 {print $0} 'example.txtawk [- F field-separator]' commands' input-file (s)

4.strut common interceptor

Comparison of filter (function callback) and interceptor (based on reflection and proxy) ActionInvocation.invoke () and access control

5. When does reflection usually be used?

When you can't get the full interface definition of the target class at the time of development, you can only integrate it according to the naming rules.

And can be extended to the application of packaging, dynamic agent and other modes.

Sometimes I do some hack things, such as bypassing the private protection mechanism.

Reflection can abstract a lot of business logic to form a common method. This is why many frameworks use reflection.

Reflection is not used much, and you don't need it most of the time. But:

File manipulation API is not used much, but you can't do without it when you have business needs.

Threads don't use much, but sometimes it's almost impossible to run without threads.

LinkedList is not used much either, but in some cases it is dozens of times more efficient than ArrayList

TreeMap (sorted by default by key) is not used much either, but sometimes it can simplify your code

Interface (interface) is not necessary, you can do almost all the functions without writing interface.

Even, object-oriented is not necessary. You can use procedural code to accomplish functions that others do with dozens of classes.

The knowledge is your own, so why make it look like you are forced to learn? the time for asking this question is over.

P.S. Let me add:

For J2EE, ORM such as Hibernate are all based on dynamic bytecode and reflection technology, IoC frameworks such as Spring are also based on dynamic proxy (sometimes dynamic bytecode) and reflection technology, and all kinds of popular MVC are also the implementation of Servlet+ reflection.

For Android, its own Context.startActivity/sendBroadcast is based on reflection, and JSON-ORM such as Gson/Jackson is based on reflection. Reflection technology can also solve some cross-process call problems and system hack.

6.JVM garbage collection algorithm

Root search:

Start the search down by selecting some root objects as the starting point, if an object goes to the root object

When unreachable, the object is no longer referenced and can be recycled. Can be used as a root.

Objects are: objects referenced by variables in the stack, objects referenced by static properties of classes, objects referenced by constants, and so on.

Because each thread has a stack, we need to select multiple root objects.

1. Mark-clear algorithm (Mark-Sweep)

two。 Replication algorithm (Copying)

3. Tag-collation algorithm (Mark-Compact)

7.mysqldump backup database

Execute the following command under linux shell to back up the database

Mysqldump-hhostname-uroot-p customer (database name) > backup.sql

Reduction

Mysqldump-hhostname-uroot-p customer (database name) < backup.sql

Cache cache area

Buffer buffers are generally used to write to disk

Html5 type declaration

At this point, the study on "how to write a linux script to extract rows that meet certain conditions" is over. I hope to be able to solve your doubts. The collocation of theory and practice can better help you learn, go and try it! If you want to continue to learn more related knowledge, please continue to follow the website, the editor will continue to work hard to bring you more practical articles!

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