Formatted strings are composed of placeholders and normal characters.
Placeholder starts with '%' and ends with verb.
Placeholders are composed of five types of elements: flags, width, precision, parameter index, and verbs.
Except for the last verb, all other elements can be omitted.
See the following example description of common types:
Default format and type
Value: []int64{0, 1}
| Formatted effects | verb | describe |
|---|---|---|
| [0 1] | %v | Default format |
| []int64{0, 1} | %#v | go syntax printing |
| []int64 | %T | Type Print |
Integer (indent, binary type, positive and negative symbol)
Value: 15
| Formatted effects | verb | describe |
|---|---|---|
| 15 | %d | Decimal |
| +15 | %+d | Positive and negative symbols must be displayed |
| ␣␣15 | %4d | Pad space (width is 4, right-aligned) |
| 15␣␣ | %-4d | Pad space (width is 4, left aligned) |
| 0015 | %04d | Pad space (width is 4) |
| 1111 | %b | Binary |
| 17 | %o | Octal |
| f | %x | Hexadecimal, lowercase |
| F | %X | Hexadecimal, capital |
| 0xf | %#x | Hexadecimal, with the digit 0x |
Characters (with quotes, Unicode)
Value: 65 (Unicode letter A)
| Formatted effects | verb | describe |
|---|---|---|
| A | %c | character |
| 'A' | %q | Characters with quotes |
| U+0041 | %U | Unicode |
| U+0041 'A' | %#U | Unicode has quotes |
Boolean(true/false)
Use %t to format a boolean type to true or false
Pointer (hex)
Use %p to format a pointer to hexadecimal display method
Floating point (indent, precision, scientific counting)
Value: 123.456
| Formatted effects | verb | describe |
|---|---|---|
| 1.234560e+02 | %e | Scientific Counting |
| 123.456000 | %f | Decimal decimal |
| 123.46 | %.2f | Default width, accuracy is 2 |
| ␣␣123.46 | %8.2f | Width is 8 and accuracy is 2 |
| 123.456 | %g | Select %e or %f according to the situation, and there is no 0 at the end |
String or byte slice (quotation marks, indentation, hexadecimal)
Value: "café"
| Formatted effects | verb | describe |
|---|---|---|
| café | %s | String output as is |
| ␣␣café | %6s | Width is 6, right-aligned |
| café␣␣ | %-6s | Width is 6, left aligned |
| "café" | %q | Quoted strings |
| 636166c3a9 | %x | Print each byte in hexadecimal form |
| 63 61 66 c3 a9 | % x | Print each byte in hexadecimal form, with spaces between bytes |
Supplement: Format symbol description in golang
The default format representation of the %v value
%+v is similar to %v, but the field name will be added when outputting the structure
Go syntax representation of %#v value
Go syntax representation of the type of %T value
%% percent sign
Boolean value:
%t word true or false
Integer:
%b is expressed as binary
%c The unicode code value corresponding to this value
%d is decimal
%o is expressed as octal
%q The literal value of the go syntax character enclosed in single quotes corresponding to this value will be safely escaped if necessary
%x is expressed in hexadecimal, using a-f
%X is expressed in hexadecimal, using A-F
%U is expressed in Unicode format: U+1234, equivalent to "U+%04X"
Two components of floating point numbers and complex numbers:
%b Scientific notation method without decimal parts and binary indexes, such as -123456p-78; see
%e Scientific notation method, such as -1234.456e+78
%E Scientific notation method, such as -1234.456E+78
%f has a decimal part but no exponential part, such as 123.456
%F is equivalent to %f
%g adopts %e or %f format according to actual conditions (for a more concise and accurate output)
%G adopts %E or %F format according to actual conditions (for a more concise and accurate output)
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