scanf

Syntax

#include <stdio.h>

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

Description

This function scans formatted text from stdin and stores it in the variables pointed to by the arguments. See section scanf.

The format string contains regular characters which much match the input exactly as well as a conversion specifiers, which begin with a percent symbol. Any whitespace in the format string matches zero or more of any whitespace characters in the input. Thus, a single space may match a newline and two tabs in the input. All conversions except c and [ also skip leading whitespace automatically. Each conversion specifier contains the following fields:

• An asterisk (*) which indicates that the input should be converted according to the conversion spec, but not stored anywhere.
• A width specifier, which specifies the maximum number of input characters to use in the conversion.
• An optional conversion qualifier, which may be h to specify short, l to specify doubles or long ints or, or L to specify long doubles. Long long type can be specified by L or ll.
• The conversion type specifier:

  c

  Copy the next character (or width characters) to the given buffer.

  d

  Convert the input to a signed integer.

  e

  E

  f

  g

  G

  Convert the input to a floating point number.

  i

  Convert the input, determining base automatically by the presence of 0x or 0 prefixes. See section strtol.

  n

  Store the number of characters scanned so far into the integer pointed to.

  o

  Convert the input to a signed integer, using base 8.

  p

  Convert the input to a pointer. This is like using the x format.

  s

  Copy the input to the given string, skipping leading whitespace and copying non-whitespace characters up to the next whitespace. The string stored is then NULL-terminated.

  u

  Convert the input to an unsigned integer.

  x

  X

  Convert the input to an unsigned integer, using base 16.

  [...]

  Like the c format, except only certain characters are copied. The characters between the brackets determine which characters are allowed, and thus when the copying stops. These characters may be regular characters (example: [abcd]) or a range of characters (example: [a-d]). If the first character is a caret (^), then the set specifies the set of characters that do not get copied (i.e. the set is negated). To specify that the set contains a close-bracket (]), list that as the first regular character.

  %

  This must match a percent character in the input.

Most conversions make use of strtol or strtoul to perform the actual conversions.

Return Value

The number of items successfully matched and assigned. If input ends before first item is assigned, EOF is returned.

Portability

ANSI, POSIX

Example

int x, y;
char buf[100];
scanf("%d %d %s", &x, &y, buf);

/* read to end-of-line */
scanf("%d %[^\n]\n", &x, buf);
/* read letters only */
scanf("[a-zA-Z]", buf);

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