unixdev.net


Switch to SpeakEasy.net DSL

The Modular Manual Browser

Home Page
Manual: (4.2BSD)
Page:
Section:
Apropos / Subsearch:
optional field

PRINTF(3S)                                                          PRINTF(3S)



NAME
       printf, fprintf, sprintf - formatted output conversion

SYNOPSIS
       #include <&lt;stdio.h>&gt;

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

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

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

       #include <&lt;varargs.h>&gt;
       _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  %.   Fol-
       lowing the %, there may be

       o      an  optional  minus  sign `-' which specifies left adjustment of
              the converted value in the indicated field;

       o      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;

       o      an optional period `.'  which serves to separate the field width
              from the next digit string;

       o      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;

       o      an  optional  `#'  character specifying that the value should be
              converted to an ``alternate form''.  For c, d, s, and u, conver-
              sions, this option has no effect.  For o conversions, the preci-
              sion 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.

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

       o      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 specifica-
              tion 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.



                                 1 April 1981                       PRINTF(3S)