NAME

printf, fprintf, sprintf, vprintf, vfprintf, vsprintf - formatted output conversion

SYNOPSIS

cc [ flag... ] file ... -lucb
#include <stdio.h>
int printf(format [ , arg ] ... )
char *format;
int fprintf(stream, format [ , arg ] ... )
FILE *stream;
char *format;
char *sprintf(s, format [ , arg ] ... )
char *s, *format;
int vprintf(format, ap)
char *format;
va_list ap;
int vfprintf(stream, format, ap)
FILE *stream;
char *format;
va_list ap;
char *vsprintf(s, format, ap)
char *s, *format;
va_list ap;

DESCRIPTION

printf places output on the standard output  stream  stdout.
fprintf  places  output on the named output stream.  sprintf
places ``output,'' followed by the NULL character  (\0),  in
consecutive bytes starting at *s; it is the user's responsi-
bility to ensure that enough storage is available.  vprintf,
vfprintf,  and vsprintf are the same as printf, fprintf, and
sprintf respectively, except that instead  of  being  called
with a variable number of arguments, they are called with an
argument list as defined by varargs(5).  Each of these func-
tions  converts,  formats, and prints its args under control
of the format.  The format is a character string which  con-
tains  two  types  of  objects:  plain characters, which are
simply copied to the output stream, and conversion  specifi-
cations,  each  of  which  causes conversion and printing of
zero or more args.  The results are undefined if  there  are
insufficient   args  for  the  format.   If  the  format  is
exhausted while args remain,  the  excess  args  are  simply
ignored.  Each conversion specification is introduced by the
character %.  After the %, the following appear in sequence:
     Zero or more flags, which modify  the  meaning  of  the
     conversion  specification.   An  optional decimal digit
     string specifying a minimum field width.  If  the  con-
     verted value has fewer characters than the field width,
     it will be padded on the left (or right, if  the  left-
     adjustment  flag  `-', described below, has been given)
     to the field width.  The padding is with blanks  unless
     the  field  width  digit  string starts with a zero, in
     which case the padding is with zeros.  A precision that
     gives the minimum number of digits to appear for the d,
     i, o, u, x, or X conversions, the number of  digits  to
     appear  after  the  decimal  point  for the e, E, and f
     conversions, the maximum number of  significant  digits
     for  the  g  and G conversion, or the maximum number of
     characters to be printed from a string in s conversion.
     The  precision takes the form of a period (.)  followed
     by a decimal digit  string;  a  NULL  digit  string  is
     treated  as  zero.  Padding specified  by the precision
     overrides the padding specified by the field width.  An
     optional  l  (ell) specifying that a following d, i, o,
     u, x, or X  conversion  character  applies  to  a  long
     integer  arg.  An l before any other conversion charac-
     ter is ignored.  A character that indicates the type of
     conversion to be applied.
A field width or precision or both may be  indicated  by  an
asterisk  (*)  instead  of a digit string.  In this case, an
integer arg supplies the field width or precision.  The  arg
that  is actually converted is not fetched until the conver-
sion letter is seen, so the args specifying field  width  or
precision  must  appear  before  the arg (if any) to be con-
verted.  A negative field width argument is taken as  a  `-'
flag  followed  by a positive field width.  If the precision
argument is negative, it will be changed to zero.  The  flag
characters and their meanings are:
-         The  result  of  the  conversion  will  be   left-
          justified within the field.
+         The result of  a  signed  conversion  will  always
          begin with a sign (+ or -).
blank     If the first character of a signed  conversion  is
          not  a  sign,  a  blank  will  be  prefixed to the
          result.  This implies that  if  the  blank  and  +
          flags both appear, the blank flag will be ignored.
#         This flag specifies that the value is to  be  con-
          verted  to  an  ``alternate form.''For c, d, i, s,
          and u conversions, the flag has no effect.  For  o
          conversion,  it  increases  the precision to force
          the first digit of the result to be a zero.  For x
          or X conversion, a non-zero result will have 0x or
          0X prefixed to it.  For e, E, f, g, and G  conver-
          sions,  the  result  will always contain a decimal
          point, even if no digits follow  the  point  (nor-
          mally,  a  decimal  point appears in the result of
          these conversions only if  a  digit  follows  it).
          For  g and G conversions, trailing zeroes will not
          be removed from the result  (which  they  normally
          are).   The  conversion characters and their mean-
          ings are:
d,i,o,u,x,X
          The integer arg is converted to signed decimal  (d
          or  i),  unsigned octal (o), unsigned decimal (u),
          or  unsigned  hexadecimal  notation  (x  and   X),
          respectively;  the  letters  abcdef are used for x
          conversion and the letters ABCDEF  for  X  conver-
          sion.   The precision specifies the minimum number
          of digits to appear; if the value being  converted
          can  be  represented  in  fewer digits, it will be
          expanded with leading zeroes.  (For  compatibility
          with  older  versions, padding with leading zeroes
          may alternatively be  specified  by  prepending  a
          zero  to  the field width.  This does not imply an
          octal value for the  field  width.)   The  default
          precision  is  1.  The result of converting a zero
          value with a precision of zero is a NULL string.
f         The float or double arg is  converted  to  decimal
          notation  in the style [-]ddd.ddd where the number
          of digits after the decimal point is equal to  the
          precision  specification.   If  the  precision  is
          missing, 6 digits are given; if the  precision  is
          explicitly  0,  no digits and no decimal point are
          printed.
e,E       The float or double arg is converted in the  style
          [-]d.ddde_ddd, where there is one digit before the
          decimal point and the number of digits after it is
          equal  to  the  precision;  when  the precision is
          missing, 6 digits are produced; if  the  precision
          is  zero,  no decimal point appears.  The E format
          code will produce a number with  E  instead  of  e
          introducing  the  exponent.   The  exponent always
          contains at least two digits.
g,G       The float or double arg is printed in style f or e
          (or  in  style  E in the case of a G format code),
          with the precision specifying the number of signi-
          ficant  digits.   The  style  used  depends on the
          value converted:  style e or E will be  used  only
          if  the  exponent resulting from the conversion is
          less  than  -4  or  greater  than  the  precision.
          Trailing  zeroes  are  removed  from the result; a
          decimal point appears only if it is followed by  a
          digit.   The  e, E, f, g, and G formats print IEEE
          indeterminate values (infinity or not-a-number) as
          ``Infinity'' or ``NaN'' respectively.
c         The character arg is printed.
s         The  arg  is  taken  to  be  a  string  (character
          pointer)   and  characters  from  the  string  are
          printed until a NULL character (\0) is encountered
          or until the number of characters indicated by the
          precision specification is reached.  If the preci-
          sion  is  missing,  it is taken to be infinite, so
          all characters up to the first NULL character  are
          printed.   A  NULL  value for arg will yield unde-
          fined results.

% Print a %; no argument is converted. In no case does a non-existent or small field width cause truncation of a field; if the result of a conversion is wider than the field width, the field is simply expanded to contain the conversion result. Padding takes place only if the specified field width exceeds the actual width. Characters generated by printf and fprintf are printed as if putc(3S) had been called.

RETURN VALUE

Upon success, printf and fprintf return the number of characters transmitted, excluding the null character. vprintf and vfprintf return the number of characters transmitted. sprintf and vsprintf always return s. If an output error is encountered, printf, fprint, vprintf, and vfprintf, return EOF.

EXAMPLE

To print a date and time  in  the  form  ``Sunday,  July  3,
10:02,''  where  weekday  and  month  are  pointers to NULL-
terminated strings:
     printf("%s, %s %i, %d:%.2d", weekday, month, day, hour, min);
To print pi to 5 decimal places:
     printf("pi = %.5f", 4 * atan(1. 0));

SEE ALSO

econvert(3) putc(3S), scanf(3S), varargs(5), vprintf(3S)  in
the Programmer's Reference Manual.

NOTES

Very wide fields (>128 characters) fail.