printf

Syntax

#include <stdio.h> int printf(const char *format, ...);

Description

Sends formatted output from the arguments (...) to stdout.

The format string contains regular characters to print, as well as conversion specifiers, which begin with a percent symbol. Each conversion speficier contains the following fields:

• an optional flag, which may alter the conversion:

  -

  left-justify the field.

  +

  Force a + sign on positive numbers.

  space

  To leave a blank space where a plus or minus sign would have been.

  #

  Alternate conversion - prefix octal numbers with 0, hexadecimal numbers with 0x or 0X, or force a trailing decimal point if a floating point conversion would have omitted it.

  0

  To pad numbers with leading zeros.

• A field width specifier, which specifies the minimum width of the field. This may also be an asterisk (*), which means that the actual width will be obtained from the next argument. If the argument is negative, it supplies a - flag and a positive width.

• An optional decimal point and a precision. This may also be an asterisk, but a negative argument for it indicates a precision of zero. The precision specifies the minimum number of digits to print for an integer, the number of fraction digits for a floating point number (max for g or G, actual for others), or the maximum number of characters for a string.

• An optional conversion qualifier, which may be:

  hh

  to specify char;

  h

  to specify short integers;

  j

  to specify intmax_t or uintmax_t integers;

  l

  to specify doubles or long integers;

  ll

  (two lower-case ell letters) to specify long long integers; to specify long doubles, although this is non-standard;

  L

  to specify long doubles;

  t

  to specify ptrdiff_t;

  z

  to specify size_t.

• The conversion type specifier:

  c

  A single character.

  d

  A signed integer.

  D

  A signed long integer. This is non-standard and obsolete. Please use ld instead.

  e

  E

  A floating point number (float or double). For long double, use "Le" or "LE". The exponent case matches the specifier case. The representation always has an exponent.

  f

  A floating point number (float or double). For long double, use "Lf". The representation never has an exponent.

  g

  G

  A floating point number (float or double). For long double, use "Lg" or "LG". The exponent case matches the specifier case. The representation has an exponent if it needs one.

  i

  A signed integer.

  n

  The next argument is a pointer to an integer, and the number of characters generated so far is stored in that integer.

  o

  A unsigned integer, printed in base 8 instead of base 10.

  O

  A unsigned long integer, printed in base 8 instead of base 10. This is non-standard and obsolete. Please use lo instead.

  p

  A pointer. This is printed with an x specifier.

  s

  A NULL-terminated string.

  u

  An unsigned integer.

  U

  An unsigned long integer. This is non-standard and obsolete. Please use lu instead.

  x

  X

  An unsigned integer, printed in base 16 instead of base 10. The case of the letters used matches the specifier case.

  %

  A single percent symbol is printed.

Return Value

The number of characters written.

Portability

ANSI/ISO C	C89; C99 (see note 1) (see note 2)
POSIX	1003.2-1992; 1003.1-2001

Notes:

1. The hh, j, t and z conversion specifiers first appeared in the ANSI C99 standard.

2. The D, O and U conversion types are non-standard. gcc may generate warnings, if you use them.

Example

printf("%-3d %10.2f%% Percent of %s\n", index, per[index], name[index]);