


      PRINTF(3S)                  (UNIX 5.0)                 PRINTF(3S)



      NAME
           printf, fprintf, sprintf - print formatted output

      SYNTAX
           #include <stdio.h>

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

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

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

      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
           responsibility to ensure that enough storage is available.
           Each function returns the number of characters transmitted
           (not including the \0 in the case of sprintf), or a negative
           value if an output error was encountered.

           Each of these functions converts, formats, and prints its
           args under control of the format.  The format is a character
           string that contains two types of objects:  plain
           characters, which are simply copied to the output stream,
           and conversion specifications, each of which results in
           fetching 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 converted value has fewer
                characters than the field width, it will be padded on
                the left (or right, if the left-adjustment flag (see
                below) has been given) to the field width;

                A precision that gives the minimum number of digits to
                appear for the d, o, u, x, or X conversions, the number
                of digits to appear after the decimal point for the e
                and f conversions, the maximum number of significant



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                digits for the 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.

                An optional l specifying that a following d, o, u, x,
                or X conversion character applies to a long integer
                arg.

                A character that indicates the type of conversion to be
                applied.

           A field width or precision 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 conversion
           letter is seen, so the args specifying field width or
           precision must appear before the arg (if any) to be
           converted.

           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
                     converted to an ``alternate form.''For c, d, 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
                     (X) conversion, a non-zero result will have 0x
                     (0X) prefixed 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 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 meanings are:

           d,o,u,x,X The integer arg is converted to signed decimal,
                     unsigned octal, decimal, or hexadecimal notation
                     (x and X), respectively; the letters abcdef are
                     used for x conversion and the letters ABCDEF for X
                     conversion.  The precision specifies the minimum



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                     number of digits to appear; if the value being
                     converted can be represented in fewer digits, it
                     will be expanded with leading zeroes.  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 output; if the precision
                     is explicitly 0, no decimal point appears.
           e,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 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
                     significant digits.  The style used depends on the
                     value converted:  style 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.
           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 the number of characters indicated by the
                     precision specification is reached.  If the
                     precision is missing, it is taken to be infinite,
                     so all characters up to the first null character
                     are printed.  If the string pointer arg has the
                     value zero, the result is undefined.  A null arg
                     will yield undefined 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.  Characters generated by
           printf and fprintf are printed as if putc(3S) had been
           called.

      EXAMPLES
           To print a date and time in the form ``Sunday, July 3,
           10:02'', where weekday and month are pointers to null-



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           terminated strings:

                printf("%s, %s %d, %.2d:%.2d", weekday, month, day, hour, min);

           To print pi to 5 decimal places:

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

      SEE ALSO
           ecvt(3C), putc(3S), scanf(3S), stdio(3S).













































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