4.3BSD - /usr/man/cat3/printf.0

PRINTF(3S)                                                          PRINTF(3S)


NAME
       printf, fprintf, sprintf - formatted output conversion

SYNOPSIS
       #include <stdio.h>

       printf(format [, arg ] ...  )
       char *format;

       fprintf(stream, format [, arg ] ...  )
       FILE *stream;
       char *format;

       sprintf(s, format [, arg ] ...  )
       char *s, format;

       #include <varargs.h>
       _doprnt(format, args, stream)
       char *format;
       va_list *args;
       FILE *stream;

DESCRIPTION
       Printf  places  output  on  the standard output stream stdout.  Fprintf
       places output on the named output stream.  Sprintf places  ‘output’  in
       the  string  s,  followed by the character ‘\0’.  All of these routines
       work by calling the internal routine _doprnt, using the variable-length
       argument facilities of varargs(3).

       Each  of  these  functions  converts, formats, and prints its arguments
       after the first under control of the first argument.  The  first  argu‐
       ment  is  a character string which contains two types of objects: plain
       characters, which are simply copied to the output stream,  and  conver‐
       sion  specifications,  each  of which causes conversion and printing of
       the next successive arg printf.

       Each conversion specification is introduced by the  character  %.   The
       remainder  of  the  conversion  specification includes in the following
       order

       ··      Zero or more of following flags:

              ··      a ‘#’ character specifying that the value should be  con‐
                     verted  to  an  ‘‘alternate  form’’.  For c, d, s, and u,
                     conversions, this option has no effect.   For  o  conver‐
                     sions,  the precision of the number is increased to force
                     the first character of the output string to a zero.   For
                     x(X)  conversion, a non-zero result has the string 0x(0X)
                     prepended to it.  For e, E, f, g, and G, conversions, the
                     result  will  always  contain a decimal point, even if no
                     digits follow the point (normally, a decimal  point  only
                     appears  in  the  results of those conversions if a digit
                     follows the decimal point).  For  g  and  G  conversions,
                     trailing  zeros  are  not removed from the result as they
                     would otherwise be.

              ··      a minus sign ‘-’ which specifies left adjustment  of  the
                     converted value in the indicated field;

              ··      a  ‘+’ character specifying that there should always be a
                     sign placed before the number when using  signed  conver‐
                     sions.

              ··      a  space  specifying that a blank should be left before a
                     positive number during a signed conversion.  A ‘+’  over‐
                     rides a space if both are used.

       ··      an  optional  digit string specifying a field width; if the con‐
              verted value has fewer characters than the field width  it  will
              be  blank-padded  on  the left (or right, if the left-adjustment
              indicator has been given) to make up the  field  width;  if  the
              field  width  begins  with  a  zero,  zero-padding  will be done
              instead of blank-padding;

       ··      an optional period ‘.’  which serves to separate the field width
              from the next digit string;

       ··      an  optional digit string specifying a precision which specifies
              the number of digits to appear after the decimal point,  for  e-
              and  f-conversion,  or  the  maximum  number of characters to be
              printed from a string;

       ··      the character l specifying that a following d, o, x, or u corre‐
              sponds to a long integer arg.

       ··      a  character  which  indicates  the  type  of  conversion  to be
              applied.

       A field width or precision may be ‘*’ instead of a  digit  string.   In
       this case an integer arg supplies the field width or precision.

       The conversion characters and their meanings are

       dox    The  integer  arg is converted to decimal, octal, or hexadecimal
              notation respectively.

       f      The float or double arg is converted to decimal notation in  the
              style  ‘[-]ddd.ddd’  where  the  number of d’s after the decimal
              point is equal to the precision specification for the  argument.
              If  the  precision is missing, 6 digits are given; if the preci‐
              sion is explicitly  0,  no  digits  and  no  decimal  point  are
              printed.

       e      The float or double arg is converted in the style ‘[-]d.ddde±dd’
              where there is one digit before the decimal point and the number
              after  is equal to the precision specification for the argument;
              when the precision is missing, 6 digits are produced.

       g      The float or double arg is printed in style d, in style f, or in
              style e, whichever gives full precision in minimum space.

       c      The character arg is printed.

       s      Arg  is  taken to be a string (character pointer) and characters
              from the string are printed until a null character or until  the
              number of characters indicated by the precision specification is
              reached; however if the precision is 0 or missing all characters
              up to a null are printed.

       u      The  unsigned  integer  arg  is converted to decimal and printed
              (the result will be  in  the  range  0  through  MAXUINT,  where
              MAXUINT equals 4294967295 on a VAX-11 and 65535 on a PDP-11).

       %      Print a ‘%’; no argument is converted.

       In no case does a non-existent or small field width cause truncation of
       a field; padding takes place only if the specified field width  exceeds
       the  actual  width.   Characters  generated  by  printf  are printed by
       putc(3S).

       Examples
       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 %d, %02d:%02d", weekday, month, day, hour, min);

       To print pi to 5 decimals:

              printf("pi = %.5f", 4*atan(1.0));

SEE ALSO
       putc(3S), scanf(3S), ecvt(3)

BUGS
       Very wide fields (>128 characters) fail.


7th Edition                      June 5, 1986                       PRINTF(3S)