What are the commonly used built-in packages in Go language?

Commonly used built-in packages: 1. fmt, which can realize formatted standard input and output; 2. io; 3. bufio; 4. sort; 5. strconv; 6. os; 7. sync; 8. flag ; 9. encoding/json; 10. html/template; 11. net/http; 12. reflect; 13. os/exec; 14. strings; 15. bytes; 16. log; 17. time; 18. regexp.

The operating environment of this tutorial: Windows 7 system, GO version 1.18, Dell G3 computer.

The standard library of Go language covers various aspects such as network, system, encryption, encoding, graphics, etc. You can directly use the http package of the standard library to send and receive the HTTP protocol; the network library is based on the high-performance operating system communication model (epoll for Linux, IOCP for Windows); all encryption and encoding are supported built-in, and there is no need to obtain them from third-party developers.

The compiler of the Go language is also part of the standard library. It scans the source code through the lexicon and uses the syntax tree to obtain the source code logical branches, etc. The peripheral tools of the Go language are also built on these standard libraries. Almost most of the requirements can be fulfilled on the standard library.

Most of Golang's built-in packages will be automatically installed into the system when installing Go. We can view these packages in the $GOROOT/src/pkg directory.

Commonly used built-in packages in Go language

1) fmt

fmt package implements the format Standard input and output, which is similar to printf and scanf in C language. Among them, fmt.Printf() and fmt.Println() are the most frequently used functions by developers.

Formatting phrases are derived from the C language. Some phrases (%- sequences) are used like this:

• ##%v: The default format value. When printing the structure, the plus sign (% v) will add the field name;

• %#v: Go style value expression;

• %T: Go-style value expression with type.

2) io

This package provides the original I/O operation interface. Its main task is to encapsulate primitive I/O such as the os package, and add some other related functions to make it have abstract functions for use on public interfaces.

3) bufio

The bufio package provides a data buffering function by encapsulating the io package, which can reduce the overhead caused by reading and writing large blocks of data to a certain extent.

A buffer is maintained inside each component of bufio, and data reading and writing operations are performed directly through the buffer area. When a read or write operation is initiated, it will first try to obtain data from the buffer. Only when there is no data in the buffer, the data will be obtained from the data source and the buffer will be updated.

4) sort

sort package provides functions for sorting slices and user-defined collections.

5) strconv

The strconv package provides functions for converting strings to basic data types, or from basic data types to strings.

6) os

The os package provides a platform-independent operating system function interface, designed like Unix style, but error handling is go style. When the os package is used When failed, the error type is returned instead of the error number.

7) The sync

sync package implements multi-thread locking mechanism and other synchronization mutual exclusion mechanisms.

8) flag

#flag package provides the function of rule definition of command line parameters and parsing of incoming parameters. Most command line programs require this package.

9) encoding/json

JSON is currently widely used as a communication format in network programs. The encoding/json package provides basic support for JSON, such as serializing from an object to a JSON string, or deserializing a specific object from a JSON string.

10) html/template

Mainly implements some functions for generating html templates in web development.

11) net/http

net/http package provides HTTP related services, mainly including http request, response and URL parsing, as well as basic http client and Extended http service.

With the net/http package, you can implement a crawler or a Web server with just a few lines of code, which is unimaginable in traditional languages.

12) reflect

The reflect package implements runtime reflection, allowing programs to manipulate objects through abstract types. It is usually used to process the value of static type interface{} and parse its dynamic type information through Typeof, usually returning an object with interface type Type.

13) os/exec

The os/exec package provides related implementations for executing custom linux commands.

14) strings

The strings package is mainly a collection of functions for processing strings, including merging, searching, splitting, comparing, suffix checking, indexing, and case processing etc.

The function interface functions of the strings package and the bytes package are basically the same.

15) bytes

The bytes package provides a series of functions for reading and writing byte slices. There are many functions for byte slicing processing, which are divided into basic processing functions, comparison functions, suffix checking functions, index functions, split functions, case processing functions and sub-slicing processing functions.

16) The log

log package is mainly used to output logs in the program.

The log package provides three types of log output interfaces, Print, Fatal and Panic.

Print is normal output;

• Fatal is after executing Print, execute os.Exit(1);

• Panic calls the panic() method after executing Print.

17)time

time package is mainly used for time-related operations, such as formatting time and converting time to timestamp. Operations such as converting timestamps to time strings.

18)regexp

Encapsulation of regular expressions.

【Related recommendations: Go video tutorial, Programming teaching】

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