printf/man_3_printf at master · chingling008/printf · GitHub

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# NAME

printf - improved printf function

# SYNOPSIS

#include <unistd.h>
#include "main.h"

int _printf(const char *format, ...);

# DESCRIPTION

The   _printf   function is used to produce formatted output according to a given format string. It supports various conversion specifiers and flags.

The function takes a format string as its argument, which can contain plain characters and format specifiers. The format specifiers start with a '%' character and are followed by optional flags, field width, precision, and length modifiers, and a conversion specifier.

The function uses the   va_list   type to handle variable arguments. It retrieves the arguments based on the conversion specifiers in the format string.

The function returns the number of characters printed on success, or -1 on error.

# FORMAT SPECIFIERS

The following format specifiers are supported by the   _printf   function:

-   %c  : Prints a single character.
-   %s  : Prints a null-terminated string.
-   %d   or   %i  : Prints a signed decimal integer.
-   %u  : Prints an unsigned decimal integer.
-   %o  : Prints an unsigned octal integer.
-   %x  : Prints an unsigned hexadecimal integer in lowercase.
-   %X  : Prints an unsigned hexadecimal integer in uppercase.
-   %p  : Prints the address of a variable in hexadecimal format.
-   %r  : Prints a string in reverse.
-   %R  : Prints a string using the ROT13 cipher.
-   %%  : Prints a percent symbol.

# FLAGS

The following flags can be used with the format specifiers:

-   -  : Left-aligns the output.
-   +  : Prints a plus sign (+) for positive numbers.
-       (space): Prints a space character for positive numbers.
-   #  : Adds a prefix (0x or 0) for non-zero values in hexadecimal, octal, or address formats.

# RETURN VALUE

The   _printf   function returns the number of characters printed on success, or -1 on error.

# EXAMPLES

#include "main.h"

int main(void)
{
    int len;

    len = _printf("Hello, %s!\n", "world");
    _printf("Length: %d\n", len);

    _printf("Decimal: %d\n", 12345);
    _printf("Octal: %o\n", 12345);
    _printf("Hexadecimal: %x\n", 12345);

    _printf("Address: %p\n", &len);

    _printf("Reverse: %r\n", "Hello");

    _printf("ROT13: %R\n", "Hello");

    _printf("Percent: %%\n");

    return (0);
}

Output:

Hello, world!
Length: 14
Decimal: 12345
Octal: 30071
Hexadecimal: 3039
Address: 0x7ffd5d4f8bdc
Reverse: olleH
ROT13: Uryyb
Percent: %