fmt.Printf format reference

Here's the fmt.Printf format reference for Go (golang):

General

the value in a default format	%v
type of the value	%T

Integer

+255	Always show sign	%+d
'ÿ'	Single quoted	%q
377	Octal without leading ‘0’	%o
0377	Octal with leading ‘0’	%#o
ff	Hex lowercase	%x
FF	Hex uppercase	%X
0xff	Hex with “0x”	%#x
U+00FF	Unicode	%U
U+00FF ‘ÿ’	Unicode with char	%#U
11111111	Binary	%b

Integer width

|    1| |   12| |  123| | 1234| |12345| |123456| |1234567|	|1    | |12   | |123  | |1234 | |12345| |123456| |1234567|	Minimum width=5. Expand if wider.	%5d %-5d (Left justify)
|    1| |   12| |  123| | 1234| |12345| |12345| |12345|	|1    | |12   | |123  | |1234 | |12345| |12345| |12345|	Width=5. Truncate right if wider.	fmt.Printf(“%s”, fmt.Sprintf(“%5d”, value)[:5])) fmt.Printf(“%s”, fmt.Sprintf(“%-5d”, value)[:5])) (Left justify)   or fmt.Printf(“|%5.5s|\n”, strconv.Itoa(value)) fmt.Printf(“|%-5.5s|\n”, strconv.Itoa(value)) (Left justify)
|    1| |   12| |  123| | 1234| |12345| |23456| |34567|	|1    | |12   | |123  | |1234 | |12345| |23456| |34567|	Width=5. Truncate left if wider.	fmt.Printf(“%5d”, val % 100000) fmt.Printf(“%-5d”, val % 100000) (Left justify)
|0012345|		Pad with ‘0’ (Right justify only)	%07d

Float

original	%f (=%.6f) 6 digits after decimal	%e (=%.6e) 6 digits after decimal	%g smallest number of digits necessary	%.3g total number of digits=3
12345 1234.5 123.45 12.345 1.2345 0.12345 0.012345 0.0012345 0.00012345 0.000012345 0.0000012345	12345.000000 1234.500000 123.450000 12.345000 1.234500 0.123450 0.012345 0.001234 0.000123 0.000012 0.000001	1.234500e+04 1.234500e+03 1.234500e+02 1.234500e+01 1.234500e+00 1.234500e-01 1.234500e-02 1.234500e-03 1.234500e-04 1.234500e-05 1.234500e-06	12345 1234.5 123.45 12.345 1.2345 0.12345 0.012345 0.0012345 0.00012345 1.2345e-05 1.2345e-06	1.23e+04 1.23e+03 123 12.3 1.23 0.123 0.0123 0.00123 0.000123 1.23e-05 1.23e-06

String

love is "愛"	Normal	%s
"love is \"愛\""	Double-quoted	%q
`love is "愛"`	Back-quoted if possible. Otherwise, double-quoted	%#q
"love is \"\u611b\""	Double-quoted. ASCII only.	%+q
6c6f76652069732022e6849b22	Hex lowercase.	%x
6C6F76652069732022E6849B22	Hex uppercase.	%X
6c 6f 76 65 20 69 73 20 22 e6 84 9b 22	Hex with space.	% x

String width

|    1| |   12| |  123| | 1234| |12345| |123456| |1234567| |12345678| |123456789| |1234567890|	|1    | |12   | |123  | |1234 | |12345| |123456| |1234567| |12345678| |123456789| |1234567890|	Minimum width=5. Expand if wider.	%5s %-5s (Left justify)
|1| |12| |123| |1234| |12345| |12345| |12345|		Maximum width=5(Expand up to 5).	%.5s
|    1| |   12| |  123| | 1234| |12345| |123456| |1234567| |1234567| |1234567| |1234567|	|1    | |12   | |123  | |1234 | |12345| |123456| |1234567| |1234567| |1234567| |1234567|	Minimum width=5. Expand up to 7.	%5.7s %-5.7 (Left justify)
|    1| |   12| |  123| | 1234| |12345| |12345| |12345|	|1    | |12   | |123  | |1234 | |12345| |12345| |12345|	Width=5.	%5.5s %-5.5s (Left justify)
|    1| |   12| |  123| |  123| |  123|	|1    | |12   | |123  | |123  | |123  |	Width=5. Truncate if wider than 3.	%5.3s %-5.3s (Left justify)
|0012345|	|12345  |	Pad with ‘0’. Doen’t work when left-justify	%07s

Struct

{sam {12345 67890}}	Normal	%v
{name:sam phone:{mobile:12345 office:67890}	With field names	%+v
main.People{name:”sam”, phone:main.Phone{mobile:”12345”, office:”67890”}}	Go’s syntax	%#v

Boolean

true false

Boolean

%t

Pointer

0x1842c220	Pointer with 0x	%p
1842c220	Pointer without 0x	%#p

References

http://golang-examples.tumblr.com/post/86795367134/fmt-printf-format-reference-cheat-sheet

Share this article

This work is licensed under the Creative Commons Attribution 3.0 Unported License.