• Linux text view command and its options (cat, head, tail)


    Linux system built-in commands can be queried in the following two ways: “cat — help” or “man cat”. The common options and official explanations of the cat command are as follows: cat file_ Name displays all the contents of the file cat -b file_ Name displays the non empty line content of the file cat […]

  • Python 3 standard library: IO text, decimal and raw stream I / O tools


    1. IO text, decimal and raw stream I / O tools The IO module implements some classes on top of the interpreter’s built-in open() to complete file based input and output operations. These classes are properly decomposed so that they can be reassembled for different purposes — for example, to support writing Unicode data to […]

  • Practice experience of IOS development with byte skipping (offered!)


    Byte bounce video side Algorithm Title: two queue simulation stacks What happened from URL input to page return This paper introduces the common sorting algorithms and their efficiency and stability C + + object oriented mechanism Encapsulation, inheritance, polymorphism The process of three handshakes Why shake hands three times Do you know about heaps and […]

  • Analysis of Python protocol


    1. Use the byte method to parse and package the protocol bin_buff = bytes() bin_buff += (0x1234).to_bytes(2, byteorder = ‘big’) bin_buff += (0x56).to_bytes(1, byteorder = ‘big’) print(‘0x%s’ % bin_ buff.hex ()) ා output 0x123456 b1 = int.from_bytes(bin_buff[1:3], byteorder = ‘big’) Print (‘0x% X ‘% B1) ා output 0x3456 2. If you press struct in C, […]

  • Java Dynamic bytecode technology is used to implement the trace function of Arthas.


    reference material ASM series detailed tutorial ASM dependency not found at compile time Used[Arthas]As you all know, Arthas is a very powerful Java diagnostic tool open source for Alibaba. Whether online or offline, we can use Arthas to analyze the thread status of the program, view the real-time running status of the JVM, print the […]

  • Integer type of MySQL data type


    You can use tinyint, smallint, mediumint, int, bigint to store integers in MySQL. They use 8, 16, 24, 32, 64 bit storage space, respectively. The integer type can select the unseigned attribute, which means that negative values are not allowed and represents an unsigned number. This can roughly double the upper limit of the integer. […]

  • Energy consumed by serial MRAM


    MR25H256It is a serial MRAM with a four pin interface of chip selection (CS), serial input (SI), serial output (so) and serial clock (SCK) using serial peripheral interface, which is logically organized as a memory array of 32kx8. SPI) bus. Serial MRAM implements a common command subset for SPI EEPROM and flash components today, allowing […]

  • Three minutes to help you distinguish the misunderstanding between MySQL and Oracle


    abstractMySQL and Oracle, don’t be so stupid. MySQL and Oracle in the development of the use is everywhere, that is a simple to understand these two fire database. Essential difference: Oracle database is an object relational database management system (charge) MySQL is an open source relational database management system (free) Database security: MySQL uses three […]

  • Truncate utf8 encoded string, specify width (not length) from first byte


    Intercepts utf8 encoded string, and specifies the width (non length) from the first byte, It is suitable for the same width interception of limited string length such as news headlines The results show that the width difference between Chinese and English is the biggest, and the larger the intercepting width is, the more obvious it […]

  • C language notes (2): data type (basic data type), type conversion (automatic conversion, cast)


    Welcome to my official account, “old notes”, or to visit my personal blog. www.yuxiaoshao.cn Can QQ exchange learning 1316677086 or join my group exchange: 901648700 share resources, exchange learning data type Can add QQ group together to learn C language 984775301Data types are a wide range of systems used to declare variables or functions of […]

  • Java class file password


    brief introduction Everything starts with javac. From that moment on, java files have changed from text files that can be distinguished by our naked eyes into cold binary files. Does it mean that we can’t learn more about Java class files? The answer is No. Machines can read, why can’t people read? As long as […]

  • Use redis to count the daily and monthly activities of users (practical version)


    There are three common methods 1、 Set set (precise, space consuming) After the user logs in, the user ID is added to the set of redis, and the set will automatically de duplicate, similar to this:> sadd users_2019_06_17 user1 (integer) 1> sadd users_2019_06_17 user2 (integer) 1> sadd users_2019_06_17 user3 (integer) 1 Obviously, […]