Skip to content

Latest commit

 

History

History
88 lines (62 loc) · 4.3 KB

202_vscanf.asciidoc

File metadata and controls

88 lines (62 loc) · 4.3 KB

vscanf

NAME

vscanf - Format input of a stdarg argument list.

SYNOPSIS
#include <stdio.h>

int vscanf(const char *restrict format, va_list arg);
DESCRIPTION

The vscanf function is equivalent to scanf, with the variable argument list replaced by arg, which shall have been initialized by the va_start macro (and possibly subsequent va_arg calls). The vscanf function does not invoke the va_end macro.

PARAMETERS

  • format - String that can contain one or more of these items:

    • Whitespace characters: the function will read and ignore any whitespace characters (this includes blank, newline and tab characters) encountered before the next non-whitespace character. This includes any quantity of whitespace characters (including none).

    • Non-whitespace characters (any character not including blank, newline, tab, or any format specifier beginning with % character): this cause that the function read and discard any character that match the given non-whitespace character. If this character is not found the function ends returning error.

    • Format specifiers: A sequence of characters beginning with '%' indicates that next data has to be read and stored at the location pointed by its corresponding argument with a given format that is specified following this prototype: %[*][width][modifiers]type where:

*

Data is read but ignored. It is not assigned to the corresponding argument.

width

Specifies the maximum number of characters to be read.

modifiers

Specifies a different size for the data pointed by argument:

- h: short int - l: long int (if integer) or double (if floating point). - L: long double

type

Character specifying the type of data that is expected and how it has to be read. See next table.
type Qualifying Input required argument

c

Single character: Reads the next character (whitespace characters included).

char *

d

Decimal integer: Number optionally preceded with a sign.

int *

e,E,f,g,G

Floating point: Decimal number containing a decimal point, optionally preceded by a sign and optionally followed by the e or E character and a decimal number. Valid entries are -732.103 or 7.12e4

float *

o

Octal integer.

int *

s

String of characters. This will read subsequent characters until a whitespace is found (whitespace characters are blank, newline and tab).

char *(string)

u

Unsigned decimal integer.

unsigned int *

x

Hexadecimal integer.

int *

argument(s) - pointer to objects or structures to be filled with data read as specified by format string. There must be the same number of these parameters than the number of format tags. NOTE: These arguments must be pointers: if you want to store the result of a scanf operation on a standard variable you should precede it with the reference operator, i.e. an ampersand sign (&), like in: scanf ("%d",&n);

RETURN VALUE

The vscanf function returns the value of the macro EOF if an input failure occurs before any conversion. Otherwise, the vscanf function returns the number of input items assigned, which can be fewer than provided for, or even zero, in the event of an early matching failure.

SEE ALSO

scanf

EXAMPLE
link:src/vscanf.c[role=include]
OUTPUT
$ gcc -Wall vscanf.c
$ ./a.out
Enter an integer, a real number, a character and a string :
42 123.456 a hello
integer = 42
real number = 123.456001
character = a
string = hello