How to use fmt.Sprintf Function in Go



Package fmt implements formatted I/O with functions analogous to C's printf and scanf. The format 'verbs' are derived from C's but are simpler.


Sprintf formats according to a format specifier and returns the resulting string.

// func Sprintf(format string, a ...interface{}) string
s := fmt.Sprintf("Apple iOS %s", "15.4")

// floating-point number
s := fmt.Sprintf("Apple iOS %f", 15.4)

// any value
s := fmt.Sprintf("Apple iOS %v", 15.4)
Apple iOS 15.4
Apple iOS 15.400000
Apple iOS 15.4


Printf formats according to a format specifier and writes to standard output. It returns the number of bytes written and any write error encountered.

// func Printf(format string, a ...interface{}) (n int, err error)
fmt.Printf("Apple iOS %s\n", "15.4")
Apple iOS 15.4

The verbs

Printf has over a dozen such conversions, which Go programmers call verbs.

The verbs:
the value in a default format when printing structs, the plus flag (%+v) adds field names
a Go-syntax representation of the value
a Go-syntax representation of the type of the value
a literal percent sign; consumes no value
the word true or false
base 2
the character represented by the corresponding Unicode code point
base 10
base 8
base 8 with 0o prefix
a single-quoted character literal safely escaped with Go syntax.
base 16, with lower-case letters for a-f
base 16, with upper-case letters for A-F
Unicode format: U+1234; same as "U+%04X"
decimalless scientific notation with exponent a power of two, in the manner of strconv.FormatFloat with the 'b' format, e.g. -123456p-78
scientific notation, e.g. -1.234456e+78
scientific notation, e.g. -1.234456E+78
decimal point but no exponent, e.g. 123.456
synonym for %f
%g %e
for large exponents, %f otherwise. Precision is discussed below.
%G %E
for large exponents, %F otherwise
hexadecimal notation (with decimal power of two exponent), e.g. -0x1.23abcp+20
upper-case hexadecimal notation, e.g. -0X1.23ABCP+20
the uninterpreted bytes of the string or slice
a double-quoted string safely escaped with Go syntax
base 16, lower-case, two characters per byte
base 16, upper-case, two characters per byte
default width, default precision
width 9, default precision
default width, precision 2
width 9, precision 2
width 9, precision 0
always print a sign for numeric values; guarantee ASCII-only output for %q (%+q)
pad with spaces on the right rather than the left (left-justify the field)
alternate format: add leading 0b for binary (%#b), 0 for octal (%#o), 0x or 0X for hex (%#x or %#X); suppress 0x for %p (%#p); for %q, print a raw (backquoted) string if strconv.CanBackquote returns true; always print a decimal point for %e, %E, %f, %F, %g and %G; do not remove trailing zeros for %g and %G; write e.g. U+0078 'x' if the character is printable for %U (%#U).
' '
(space) leave a space for elided sign in numbers (% d); put spaces between bytes printing strings or slices in hex (% x, % X)
pad with leading zeros rather than spaces; for numbers, this moves the padding after the sign

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