FPRINTF(2)                                             FPRINTF(2)

     NAME
          fprintf, printf, sprintf, snprintf, vfprintf, vprintf,
          vsprintf, vsnprintf - print formatted output

     SYNOPSIS
          #include <u.h>
          #include <stdio.h>

          int fprintf(FILE *f, char *format, ...)

          int printf(char *format, ...)

          int sprintf(char *s, char *format, ...)

          int snprintf(char *s, int n, char *format, ...)

          int vfprintf(FILE *f, char *format, va_list args)

          int vprintf(char *format, va_list args)

          int vsprintf(char *s, char *format, va_list args)

          int vsnprintf(char *s, int n, char *format, va_list args)

     DESCRIPTION
          Fprintf places output on the named output stream f (see
          fopen(2)). Printf places output on the standard output
          stream stdout. 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.  Snprintf is like sprintf but writes at most n
          bytes (including the null character) into s. Vfprintf,
          vprintf, vsnprintf, and vsprintf are the same, except the
          args argument is the argument list of the calling function,
          and the effect is as if the calling function's argument list
          from that point on is passed to the printf routines.

          Each function returns the number of characters transmitted
          (not including the \0 in the case of sprintf and friends),
          or a negative value if an output error was encountered.

          These functions convert, format, and print their trailing
          arguments under control of a format string.  The format con-
          tains two types of objects: plain characters, which are sim-
          ply copied to the output stream, and conversion specifica-
          tions, each of which results in fetching of zero or more
          arguments.  The results are undefined if there are arguments
          of the wrong type or too few arguments for the format.  If
          the format is exhausted while arguments remain, the excess
          are ignored.

     FPRINTF(2)                                             FPRINTF(2)

          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 charac-
               ters than the field width, it will be padded with
               spaces on the left (or right, if the left adjustment,
               described later, has been given) to the field width.

               An optional precision that gives the minimum number of
               digits to appear for the d, i, o, u, x, and X conver-
               sions, the number of digits to appear after the decimal
               point for the e, E, and f conversions, the maximum num-
               ber of significant digits for the g and G conversions,
               or the maximum number of characters to be written from
               a string in s conversion.  The precision takes the form
               of a period (.)  followed by an optional decimal inte-
               ger; if the integer is omitted, it is treated as zero.

               An optional h specifying that a following d, i, o, u, x
               or X conversion specifier applies to a short int or
               unsigned short argument (the argument will have been
               promoted according to the integral promotions, and its
               value shall be converted to short or unsigned short
               before printing); an optional h specifying that a fol-
               lowing n conversion specifier applies to a pointer to a
               short argument; an optional l (ell) specifying that a
               following d, i, o, u, x, or X conversion character
               applies to a long or unsigned long argument; an
               optional l specifying that a following n conversion
               specifier applies to a pointer to a long int argument;
               or an optional L specifying that a following e, E, f,
               g, or G conversion specifier applies to a long double
               argument.  If an h, l, or L appears with any other con-
               version specifier, the behavior is undefined.

               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
          int arg supplies the field width or precision.  The argu-
          ments specifying field width or precision, or both, shall
          appear (in that order) before the argument (if any) to be
          converted.  A negative field width argument is taken as a -
          flag followed by a positive field width.  A negative preci-
          sion is taken as if it were missing.

          The flag characters and their meanings are:

     FPRINTF(2)                                             FPRINTF(2)

          -         The result of the conversion is left-justified
                    within the field.
          +         The result of a signed conversion always begins
                    with a sign (+ or -).
          blank     If the first character of a signed conversion is
                    not a sign, or a signed conversion results in no
                    characters, a blank is prefixed to the result.
                    This implies that if the blank and + flags both
                    appear, the blank flag is ignored.
          #         The result is to be converted to an ``alternate
                    form.''  For o conversion, it increases the preci-
                    sion to force the first digit of the result to be
                    a zero.  For x or X conversion, a non-zero result
                    has 0x or 0X prefixed to it.  For e, E, f, g, and
                    G conversions, the result always contains a deci-
                    mal 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 zeros are not be
                    removed from the result as they normally are.  For
                    other conversions, the behavior is undefined.
          0         For d, i, o, u, x, X, e, E, f, g, and G conver-
                    sions, leading zeros (following any indication of
                    sign or base) are used to pad the field width; no
                    space padding is performed.  If the 0 and - flags
                    both appear, the 0 flag will be ignored.  For d,
                    i, o, u, x, and X conversions, if a precision is
                    specified, the 0 flag will be ignored.  For other
                    conversions, the behavior is undefined.

          The conversion characters and their meanings are:

          d,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 or X); the
                    letters abcdef are used for x conversion and the
                    letters ABCDEF for X conversion.  The precision
                    specifies the minimum number of digits to appear;
                    if the value being converted can be represented in
                    fewer digits, it is expanded with leading zeros.
                    The default precision is 1.  The result of con-
                    verting a zero value with a precision of zero is
                    no characters.
          f         The double argument is converted to decimal nota-
                    tion 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, it is taken as 6; if the precision is
                    explicitly `0', no decimal point appears.
          e,E       The double argument 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

     FPRINTF(2)                                             FPRINTF(2)

                    equal to the precision; when the precision is
                    missing, it is taken as 6; if the precision is
                    zero, no decimal point appears.  The E format code
                    produces a number with E instead of e introducing
                    the exponent.  The exponent always contains at
                    least two digits.
          g,G       The double argument is printed in style f or e (or
                    in style E in the case of a G conversion speci-
                    fier), with the precision specifying the number of
                    significant digits.  If an explicit precision is
                    zero, it is taken as 1.  The style used depends on
                    the value converted: style e is used only if the
                    exponent resulting from the conversion is less
                    than -4 or greater than or equal to the precision.
                    Trailing zeros are removed from the fractional
                    portion of the result; a decimal point appears
                    only if it is followed by a digit.
          c         The int argument is converted to an unsigned char,
                    and the resulting character is written.
          s         The argument 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 pre-
                    cision 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.  A zero value for the argument yields
                    undefined results.
          P         The void* argument is printed in an
                    implementation-defined way (for Plan 9: the
                    address as hexadecimal number).
          n         The argument shall be a pointer to an integer into
                    which is written the number of characters written
                    to the output stream so far by this call to
                    fprintf. No argument is converted.
          %         Print a %; no argument is converted.

          If a conversion specification is invalid, the behavior is
          undefined.

          If any argument is, or points to, a union or an aggregate
          (except for an array of character type using %s conversion,
          or a pointer cast to be a pointer to void using %P conver-
          sion), the behavior is undefined.

          In no case does a nonexistent or small field width cause
          truncation of a field; if the result of a conversion is
          wider than the field width, the field is expanded to contain
          the conversion result.

     SOURCE
          /sys/src/libstdio

     FPRINTF(2)                                             FPRINTF(2)

     SEE ALSO
          fopen(2), fscanf(2), print(2)

     BUGS
          There is no way to print a wide character (rune); use
          print(2) or bio(2).