Essential Go Strings  Edit on GitHub      File Issue

Format text

Go’s standard library implements C-style string formatting in the fmt package.

s := fmt.Sprintf("Hello %s", "World")
fmt.Printf("s: '%s'\n", s)
s = fmt.Sprintf("%d + %f = %d", 2, float64(3), 5)
fmt.Println(s)
s: 'Hello World'
2 + 3.000000 = 5

The first argument to fmt.Sprintf is a formatting string which defines how to format subsequent arguments. Subsequent arguments are the values that will be formatted.

fmt.Sprintf creates a formatted string.

For convenience, there’s also:

The function Sprintf formats the string in the first parameter, replacing the verbs with the values of the subsequent parameters and returns the result. Like Sprintf, the function Printf also formats but instead of returning the result it prints the string.

List of string formatting verbs

%v    // the value in a default format
        // when printing structs, the plus flag (%+v) adds field names
%#v   // a Go-syntax representation of the value
%T    // a Go-syntax representation of the type of the value
%%    // a literal percent sign; consumes no value

Boolean:

%t    // the word true or false

Integer:

%b    // base 2
%c    // the character represented by the corresponding Unicode code point
%d    // base 10
%o    // base 8
%q    // a single-quoted character literal safely escaped with Go syntax.
%x    // base 16, with lower-case letters for a-f
%X    // base 16, with upper-case letters for A-F
%U    // Unicode format: U+1234; same as "U+%04X"

Floating-point and complex constituents:

%b    // decimalless scientific notation with exponent a power of two,
        // in the manner of strconv.FormatFloat with the 'b' format,
        // e.g. -123456p-78
%e    // scientific notation, e.g. -1.234456e+78
%E    // scientific notation, e.g. -1.234456E+78
%f    // decimal point but no exponent, e.g. 123.456
%F    // synonym for %f
%g    // %e for large exponents, %f otherwise
%G    // %E for large exponents, %F otherwise

String and slice of bytes (treated equivalently with these verbs):

%s    // the uninterpreted bytes of the string or slice
%q    // a double-quoted string safely escaped with Go syntax
%x    // base 16, lower-case, two characters per byte
%X    // base 16, upper-case, two characters per byte

Pointer:

%p    // base 16 notation, with leading 0x
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