C examples for Language Basics:printf
The following table shows how the optional output flag characters affect the output.
| Character | Use |
|---|---|
| + | Ensures there's always a plus or minus sign preceding a signed output value. Only negative values have a sign by default. |
| - | left justify the output value and padded with blanks on the right. The default is right justified. |
| 0 | Sets that integer or floating point values should be padded with zeros instead of spaces to fill out the field width to the left. |
| Space | Sets that positive or zero values are preceded by a space rather than a plus sign. |
# Ensures that:
The optional field_width specifies the minimum field width for the output value.
The optional precision specifier is used with floating-point output values and consists of a period followed by an integer.
A specifier of .n indicates that n decimal places are to be output for a floating-point value.
Size Flag Characters in an Output Specification
| Flag | Effect |
|---|---|
| h | A following integer conversion specifier applies to a short or unsigned short argument. |
| hh | A following integer conversion specifier applies to a signed char or unsigned char argument. |
| l (lowercase L) | A following integer conversion specifier applies to a long or unsigned long argument. |
| ll (lowercase LL) | A following integer conversion specifier applies to a long long or unsigned long long argument. |
| j | A following integer conversion specifier applies to an intmax_t or uintmax_t argument. |
| z | A following integer conversion specifier applies to a size_t argument. |
| t | A following integer conversion specifier applies to a ptrdiff_t argument. |
| L | A following floating-point conversion specifier applies to a long double argument. |
Conversion Characters in an Output Specification
| Conversion character | Output produced |
|---|---|
| d or i | Signed decimal integer |
| o | Unsigned octal integer |
| u | Unsigned decimal integer |
| x | Unsigned hexadecimal integer with lowercase hexadecimal digits a, b, c, d, e, f |
| X | As x but with uppercase hexadecimal digits A, B, C, D, E, F |
| f or F | Signed decimal value |
| e | Signed decimal value with exponent |
| E | As e but with E for exponent instead of e |
| g | As e or f depending on size of value and precision |
| G | As g but with E for exponent values |
| a or A | Presents a double value in hexadecimal preceded by 0x or 0X and any exponent prefixed with p or P, thus: 0xh.hhhhp+/-d where h is a hexadecimal digit. |
| p | Output the value of the argument as a pointer and the value is presented in an implementation-defined way. The argument should be of type void*. |
| c | Single character or precision characters |
| s | All characters until '\0' is reached or precision characters have been output |
You can include whitespace characters in the format control string for printf().
Whitespace characters are the newline, carriage return, form-feed, space, and tab.
Some of these are represented by escape sequences and these are shown in following Table.
| Escape sequence | Description |
|---|---|
| \b | Backspace |
| \f | Form-feed or page eject |
| \n | Newline |
| \r | Carriage return (for printers) or move to the beginning of the current line for output to the screen |
| \t | Horizontal tab |
| \\ | output the backslash character, \ |
To write a % character to stdout, you use %%.