Explore the differences between different functions in the golang fmt package

golang fmt package is a standard library commonly used in Go language. It provides various mechanisms for formatting input and output. In the fmt package, there are many different functions that accomplish different tasks. This article will explore the differences between the different functions in the fmt package.

1. The difference between Println and Printf
Println and Printf are both functions that output content, but there are some basic differences between them.

Println outputs a series of values ​​to the standard output in a specified format. The function signature of Println is:

func Println(a ...interface{}) (n int, err error)

where, a...interface{} represents any number of data of any type. There is no additional formatting when using Println output, such as:

fmt.Println("Hello", "World!", 1, 2, 3)  //输出：Hello World! 1 2 3

Printf outputs the formatted string to the standard output. The function signature of Printf is:

func Printf(format string, a ...interface{}) (n int, err error)

Among them, format is the output format, and a...interface{} represents any number of data of any type. Printf will format and concatenate the formatted string and the data to be output. As shown below:

fmt.Printf("My name is %s, and I am %d years old\n", "Jack", 25)   //输出：My name is Jack, and I am 25 years old

2. The difference between Sprintf and Fprintf
Sprintf and Fprintf are also formatted output functions, but there are some differences between them.

Sprintf formats the formatted string into a string variable. The function signature of Sprintf is:

func Sprintf(format string, a ...interface{}) string

Among them, format is the output format, and a...interface{} represents any number of data of any type. Sprintf will format and concatenate the formatted string and the data to be output, and return the result to a string. As shown below:

s := fmt.Sprintf("My name is %s, and I am %d years old\n", "Jack", 25)
fmt.Println(s) //输出：My name is Jack, and I am 25 years old

Fprintf formats the formatted string into a file. The function signature of Fprintf is:

func Fprintf(w io.Writer, format string, a ...interface{}) (n int, err error)

Among them, w io.Writer represents the output target location, format is the output format, and a...interface{} represents any number of data of any type. Fprintf will format and concatenate the formatted string and the data to be output, and output the result to the specified file. As shown below:

f, err := os.Create("output.txt")
if err != nil {
    return err
}
fmt.Fprintf(f, "My name is %s, and I am %d years old\n", "Jack", 25)

3. Summary
The above four functions are all commonly used functions in the golang fmt package, but there are certain differences between them. Println and Printf are both functions that output content. Println outputs content directly, while Printf needs to format strings and data before outputting them. Sprintf and Fprintf are both formatted output functions. Sprintf outputs the formatted string to a string variable, while Fprintf outputs the formatted string to the specified file. Mastering the above content can help us better utilize these functions for daily development work.

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