Formatting with Package "fmt"

The fmt package

Here is a list of features provided by the fmt package:

• Format things like basic strings and values.
• Print data to the console.
• Collect user input from the console.
• Write into a file using a writer.
• Print error messages.

Templates

The fmt package relies on the concept of a format template. Essentially, this is only a string that contains the text we want to manage plus some placeholders called verbs that tell fmt the format and where to insert our variables.

Verbs

There are a lot of verbs that are provided by the fmt package, including:

• %v is a generic placeholder that we can use when we’re not interested in providing a particular format and the default behavior fits well.
• %T prints the provided variable’s type.
• %d prints our variable as an integer in base-10.
• %x and %X print our variable in hexadecimal format (base-16).
• %f prints a floating point number.
• %q prints a quoted string that is a string wrapped within double quotes.
• %p prints the pointer address of our variable.

Printing

The primary purpose of this package is to print a formatted output somewhere. Let’s see where we can send our data.

STDOUT

STDOUT simply means the terminal. For printing to the console, some commonly used functions are as follows:

• The fmt.Print function prints a list of variables with the default format.

1. The fmt.Printf function allows us to specify a format template.
2. The fmt.Println function is the same as fmt.Print except it inserts spaces between the variables and appends a new line at the end.